Milan's win in Madrid is one of the few upsets with both published odds and xG: Madrid had 67.8% and 2.66 xG, Milan 14.4% and 2.45 xG. Milan deserved the win but rode their luck.
Back to the trend of the day: Bayern Munich throws away a 3-0 lead and draws in Norway
Poly Rating · from the trend of the day
Biggest Upsets in Champions League History (2026)
Sheriff Tiraspol's squad was valued at about $14M and Real Madrid's at $872M, yet Sheriff won 2-1 at the Bernabéu with an 89th-minute winner.
- No. 1: Bodø/Glimt vs Inter 2026
- 8 places
01Final list
The leading AIs built their own top-ten lists independently. Above is one combined result that is easy to check: every place has a reason, the AIs that included it and, where the AIs gave one, a source.
Order: from most to least AI agreement.
A bright badge means this AI put the entry on its list. A dim badge means it did not.
- 1
Bodø/Glimt vs Inter 2026
Norwegian debutants won both legs, 5-2 on aggregate, while Inter took 30 shots at San Siro, the most in a Champions League game on Opta's record.
Included it: Claude, ChatGPT. Did not include: Gemini.In their lists: Claude: 2 · ChatGPT: 4
What each AI noted 2
- Claudeplace 2
Inter had 30 shots at San Siro, the most in a Champions League game on Opta record since 2003-04, and still lost.
Source ↗ - ChatGPTplace 4
A Norwegian debutant knocked out the previous season’s runners-up, despite Inter’s greater pedigree.
2 AIs put it here - 2
Roma vs Barcelona 2018
Roma turned a 1-4 first-leg deficit around with a 3-0 win, the winner coming in the 82nd minute. Gemini's xG of 2.37 to 0.61 says earned, but it is a single-source estimate.
Included it: ChatGPT, Gemini. Did not include: Claude.In their lists: ChatGPT: 10 · Gemini: 10
What each AI noted 2
- ChatGPTplace 10
Roma overturned a 1-4 first-leg deficit to advance on away goals, with an 82nd-minute winner.
- Geminiplace 10
Trailing 4–1 from the Camp Nou, Roma completely throttled Barcelona, limiting Messi and Suárez to zero high-danger chances to overturn a 3-goal deficit.
2 AIs put it hereno source given - 3
Lyon vs Man City 2020
Lyon won a single-match quarter-final in Lisbon 3-1. Gemini's xG (City 2.62, Lyon 0.94) points to a lucky night, and its ~3.1x value gap is an estimate.
Included it: ChatGPT, Gemini. Did not include: Claude.In their lists: ChatGPT: 7 · Gemini: 9
What each AI noted 2
- ChatGPTplace 7
Lyon reached the semi-finals by eliminating a City side widely expected to go deeper.
- Geminiplace 9
Rudi Garcia’s counter-attacking setup exposed City's high line, generating two late Moussa Dembélé goals right after Raheem Sterling’s infamous miss.
2 AIs put it hereno source given - 4
Viking vs Bayern 2026
A draw, not a win: Bayern led 3-1 and outshot Viking 28 to 8, then drew 3-3. The xG is disputed: 0.56 to 3.51 (xGscore) or 1.84 to 2.76 (Gemini, unsourced).
Included it: ChatGPT, Gemini. Did not include: Claude.In their lists: ChatGPT: 8 · Gemini: 4
What each AI noted 2
- ChatGPTplace 8
A three-goal Bayern lead ended as a draw, with the equalizer coming after Michael Olise’s dismissal.
- Geminiplace 4
Norwegian outsiders surged to an early two-goal lead, weathered a Bavarian fightback, and snatched a point against a €900M juggernaut after an 81st-minute red card.
2 AIs put it hereno source given - 5
AC Milan vs Real Madrid 2024
Opta gave Milan 14.4% and Madrid 67.8%. Milan won 3-1 at the Bernabéu with almost equal xG (2.45 against 2.66): earned, with some luck. Single source.
Included it: ChatGPT. Did not include: Claude, Gemini.In their lists: ChatGPT: 3
What each AI noted 1
- ChatGPTplace 3
Opta’s pre-match simulations gave Madrid 67.8% to win; Milan won at the Bernabéu.
Source ↗
1 AIs put it here - 6
Bodø/Glimt vs Man City 2026
Bodø/Glimt were 3-0 up by the 58th minute, before Rodri's red. Before the game, Opta's supercomputer gave them a 0.3% chance of reaching the last 16.
Included it: Claude. Did not include: ChatGPT, Gemini.In their lists: Claude: 3
What each AI noted 1
- Claudeplace 3
City were 3-0 down before Rodri's red card, which came 53 seconds after his first yellow.
Source ↗
1 AIs put it here - 7
Villarreal vs Bayern 2022
The least earned upset here: in the second leg Bayern had 23 shots to 4 and 1.37 xG to 0.72, yet Villarreal went through 2-1 on aggregate.
Included it: Claude. Did not include: ChatGPT, Gemini.In their lists: Claude: 8
What each AI noted 1
- Claudeplace 8
Bayern had 23 shots to Villarreal's 4 (22 to 4 by another count) and went out on a 1-1 draw.
Source ↗
1 AIs put it here - 8
Sporting vs Man City 2024
The 4-1 win ended City's 26-game Champions League unbeaten run, but Opta gave City only 50.1% before kick-off. By the odds, it was a smaller shock than the score suggests.
Included it: ChatGPT. Did not include: Claude, Gemini.In their lists: ChatGPT: 2
What each AI noted 1
- ChatGPTplace 2
City arrived on a 26-game Champions League unbeaten run; Sporting ended it by three goals.
Source ↗
1 AIs put it here
02Worth knowing
What the AIs noticed while building the list.
Villarreal's win over Bayern was the least earned upset: Bayern had 1.37 xG to 0.72 and 23 shots to 4.
Bodø/Glimt beat Manchester City, Atlético and Inter in 2026 and led Sporting 3-0 before losing that tie 5-3 after extra time. Opta's supercomputer had given them a 0.3% chance of reaching the round of 16.
"Biggest" lists measure different things: UEFA's list is editorial, Eurocoeff ranks by Elo gap, and Opta's odds cover only the matches it analysed.
03How we counted
In plain words, no formulas.
1The question
Top 10 Biggest Champions League Upsets: Money, Reputation and Chances Side by Side
2Why this topic
It sets money, five-year reputation, pre-match odds and the chances actually created side by side, so readers can tell a real upset from a lucky night. No single upset list or value table does that.
3Where it applies
UEFA Champions League, modern era (league phase and knockouts), where squad values and expected goals (xG) are available for both clubs
4What we looked at
- Squad market value ratio between the two clubs on matchday
- Club coefficient gap, a five-year measure of reputation
- Pre-match win probability of the underdog as the expectation baseline
- Points or goal difference the underdog actually took, compared with what the value gap and the odds predicted
- Expected goals (xG) for each side, showing whether the result came from the underdog's own chances or from the favourite's waste
- Transfermarkt — Estimated squad market value. The figure depends on the valuation date, and there is no full matchday history for every candidate.
- UEFA club coefficients — Club results over five seasons, used as a measure of reputation
- Opta Analyst predictions and supercomputer — Pre-match win and progression odds. These are published only for the matches Opta chose to analyse.
5Who ranked
The leading AIs, each building its own list of ten independently and naming a source for every place: Claude, ChatGPT, Gemini.
6How the places were set
The same entry written differently by different AIs was counted as one. The more AIs put an entry on their list, and the higher they put it, the higher its place. "AI agreement" shows how many of the AIs had it on their own list. Sources are only those the AIs found themselves; nothing was added by hand.
04Each AI's own list
🇺🇸 Claude10 places · 3 notes
The same question, answered by Claude alone. The final list above combines all the AIs.
- 1Sheriff Tiraspol 2-1 Real Madrid (2021)
A squad valued at about $14M beat one valued at $872M, with the winner scored in the 89th minute.
Source ↗ - 2Bodø/Glimt 5-2 Inter on aggregate (2026 knockout play-off)
Inter had 30 shots at San Siro, the most in a Champions League game on Opta record since 2003-04, and still lost.
Source ↗ - 3Bodø/Glimt 3-1 Manchester City (2026)
City were 3-0 down before Rodri's red card, which came 53 seconds after his first yellow.
Source ↗ - 4Rubin Kazan 2-1 Barcelona (2009)
It was Barcelona's first Champions League defeat in 10 matches, with the winner 17 minutes from time.
Source ↗ - 5BATE Borisov 3-1 Bayern Munich (2012)
Belarusian champions beat the eventual treble winners.
Source ↗ - 6Ajax 4-1 Real Madrid (2019 round of 16)
Real Madrid, three-time defending champions, lost 4-1 at home. It was their heaviest home knockout defeat in Europe.
- 7Bodø/Glimt 2-1 Atlético Madrid (2026)
The win put Bodø/Glimt into the knockout play-offs, one week after they beat Manchester City.
Source ↗ - 8Villarreal over Bayern Munich (2022 quarter-final)
Bayern had 23 shots to Villarreal's 4 (22 to 4 by another count) and went out on a 1-1 draw.
Source ↗ - 9Union Saint-Gilloise 3-1 PSV (2025-26)
The Belgian club's first Champions League win, as one of four debutants alongside Bodø/Glimt, Kairat and Pafos.
Source ↗ - 10Basel over Manchester United (2011)
The result sent Manchester United out of the Champions League group stage and into the Europa League.
Source ↗
What Claude noticed
Bodø/Glimt did the most in 2026. They beat Manchester City and Atlético, then Inter, then led Sporting 3-0, and lost the tie 5-3 after extra time. Pre-match, the Opta supercomputer gave them only a 0.3% chance of reaching the round of 16.
Villarreal's win over Bayern was the least earned upset on my list. Bayern's xG was 1.37 to 0.72, and Bayern took 23 shots to 4.
The 2025-26 league phase had four debutants (Bodø/Glimt, Kairat, Pafos, Union SG). Qarabag got the first Champions League win ever by an Azerbaijani club.
🇺🇸 ChatGPT10 places · 2 notes
The same question, answered by ChatGPT alone. The final list above combines all the AIs.
- 1Ajax 4-1 Real Madrid (2019)
The holders’ 1-2 first-leg advantage became a 5-3 aggregate exit at the Bernabéu.
Source ↗ - 2Sporting CP 4-1 Manchester City (2024)
City arrived on a 26-game Champions League unbeaten run; Sporting ended it by three goals.
Source ↗ - 3Milan 3-1 Real Madrid (2024)
Opta’s pre-match simulations gave Madrid 67.8% to win; Milan won at the Bernabéu.
Source ↗ - 4Bodø/Glimt 3-1 Inter Milan (2026)
A Norwegian debutant knocked out the previous season’s runners-up, despite Inter’s greater pedigree.
- 5Porto 1-0 Arsenal (2024)
A stoppage-time strike gave Porto the first-leg win over the reigning champions.
- 6Shakhtar Donetsk 1-0 Barcelona (2023)
A club ranked far below Barcelona by Opta’s power rankings took all three points.
Source ↗ - 7Lyon 3-1 Manchester City (2020)
Lyon reached the semi-finals by eliminating a City side widely expected to go deeper.
- 8Viking FK 3-3 Bayern Munich (2026)
A three-goal Bayern lead ended as a draw, with the equalizer coming after Michael Olise’s dismissal.
- 9Celtic 2-1 Barcelona (2012)
Barcelona had 89% possession, but Celtic’s compact defense and two goals held up.
- 10Roma 3-0 Barcelona (2018)
Roma overturned a 1-4 first-leg deficit to advance on away goals, with an 82nd-minute winner.
What ChatGPT noticed
Milan’s 3-1 win over Madrid is unusually measurable: Opta published both a 67.8% Madrid win probability and xG for each side, showing the upset was not simply a smash-and-grab.
Opta’s 50.1% City win probability against Sporting makes that result a weaker pure-probability shock than Milan beating Madrid at 14.4%. The streak and scoreline give it more historical weight.
🇺🇸 Gemini10 places
The same question, answered by Gemini alone. The final list above combines all the AIs.
- 1Sheriff Tiraspol 2–1 Real Madrid (2021)
A Moldovan debutant squad valued at barely €12 million silenced a €780 million Galáctico roster at the Bernabéu despite facing 31 shots.
- 2Celtic 2–1 Barcelona (2012)
Celtic recorded just 16.3% ball possession and completed 166 passes against prime Tiki-Taka Barcelona to seal an iconic 125th-anniversary triumph.
- 3Rubin Kazan 2–1 Barcelona (2009)
Aleksandr Ryazantsev's 30-yard screamer catalyzed a shock defeat of Guardiola’s reigning sextuple winners on Camp Nou turf.
- 4Viking FK 3–3 Bayern Munich (2026)
Norwegian outsiders surged to an early two-goal lead, weathered a Bavarian fightback, and snatched a point against a €900M juggernaut after an 81st-minute red card.
- 5Dinamo Zagreb 1–0 Chelsea (2022)
A lone breakaway goal by Mislav Oršić outmaneuvered Chelsea's record summer spenders and led to Thomas Tuchel's dismissal the very next morning.
- 6BATE Borisov 3–1 Bayern Munich (2012)
Belarusian outsiders handed Jupp Heynckes' eventual treble-winning Bayern their solitary group-stage defeat through clinical counter-attacking precision.
- 7Young Boys 2–1 Manchester United (2021)
Cristiano Ronaldo scored inside 13 minutes, but a 35th-minute red card flipped the game entirely, paving the way for a 95th-minute Swiss upset.
- 8Ajax 4–1 Real Madrid (2019)
A fearless Dutch youth side inflicted Real Madrid's worst-ever home European defeat to shatter their 1,011-day reign as Champions League holders.
- 9Lyon 3–1 Manchester City (2020)
Rudi Garcia’s counter-attacking setup exposed City's high line, generating two late Moussa Dembélé goals right after Raheem Sterling’s infamous miss.
- 10Roma 3–0 Barcelona (2018)
Trailing 4–1 from the Camp Nou, Roma completely throttled Barcelona, limiting Messi and Suárez to zero high-danger chances to overturn a 3-goal deficit.