Upset Magnets: The Least Predictable Clubs in the Big Five
Across 8,906 big-five matches the market priced underdogs well overall. A handful of clubs, led by Sassuolo and Aston Villa, broke that pattern again and again.
Every price on a 1X2 coupon is a probability with a margin attached. My job is to check whether those probabilities hold up. In this study I asked which clubs in the Premier League, La Liga, Serie A, Bundesliga and Ligue 1 most often lose as favourites or win as underdogs, measured against what their closing odds said should happen.
The headline is that the market is well calibrated as a whole. The underdog won 20.9% of all 8,906 matches, close to the 22.8% the no-margin odds implied. The interesting part is the clubs that sit well outside that average. Spotting them is the reason I run this check before anything goes on my 1X2 bet tips page.
Section ASassuolo, Reims and Everton lose as favourites far beyond their prices
This table compares how often each club was priced to lose when it started as favourite with how often it actually lost. Sassuolo sit clearly on top. They lost 37.5% of 56 league matches as favourite against a priced 27.3%, a gap of +10.2 points. Reims lost 34.5% against 26.1%, and Everton lost 33.9% against 26.8%.
These are not elite sides that occasionally slip. They are mid-table or lower clubs that the market made favourites in fixtures they could not reliably control. For a bettor, those are the short prices that deserve the most scepticism.
| Club | League | As fav | Priced to lose | Lost | Gap |
|---|---|---|---|---|---|
| Sassuolo | Serie A | 56 | 27.3% | 37.5% | +10.2 |
| Reims | Ligue 1 | 55 | 26.1% | 34.5% | +8.4 |
| Everton | Premier League | 62 | 26.8% | 33.9% | +7.1 |
| Chelsea | Premier League | 157 | 20.2% | 24.2% | +4.0 |
| Tottenham | Premier League | 116 | 22.7% | 26.7% | +4.0 |
| Rennes | Ligue 1 | 130 | 23.8% | 27.7% | +3.9 |
| Celta Vigo | La Liga | 95 | 25.0% | 28.4% | +3.4 |
| Alavés | La Liga | 47 | 26.4% | 29.8% | +3.4 |
| Union Berlin | Bundesliga | 77 | 26.7% | 29.9% | +3.2 |
| Atalanta | Serie A | 149 | 19.7% | 22.8% | +3.1 |
| Wolfsburg | Bundesliga | 80 | 27.0% | 30.0% | +3.0 |
| Valencia | La Liga | 81 | 25.4% | 28.4% | +3.0 |
Chelsea and Tottenham interest me more than their gaps of +4.0 suggest. Chelsea's figure comes from 157 matches as favourite, and Tottenham's from 116. Chelsea lost 24.2% of those games against a priced 20.2%. A modest gap that holds over a large sample tells me more than a big gap built on a few dozen games.
Section BAston Villa top the giant-killers as Lens and Brighton follow
The dumbbell chart flips the question round. It shows how often each club won as underdog compared with the chance the market gave them. Aston Villa stand out. They won 39.2% of 79 matches as underdog against a priced chance of 24.3%. Lens won 35.4% of 48 against 26.8%, and Brighton won 32.5% of 83 against 25.9%.
Look at the error bars as well as the dots. Villa's 95% range is ±10.8 points, and Lens carry the widest band on the chart at ±13.5 points.
View the data: giant-killers: underdog win rate vs priced chance
| Priced | Won | 95% range | |
|---|---|---|---|
| Aston Villa (79 as underdog) | 24.3% | 39.2% | ±10.8 |
| Lens (48 as underdog) | 26.8% | 35.4% | ±13.5 |
| Brighton (83 as underdog) | 25.9% | 32.5% | ±10.1 |
| Lazio (65 as underdog) | 26.4% | 32.3% | ±11.4 |
| Sassuolo (96 as underdog) | 23.3% | 29.2% | ±9.1 |
| Union Berlin (93 as underdog) | 24.3% | 30.1% | ±9.3 |
| Brest (112 as underdog) | 23.6% | 28.6% | ±8.4 |
| Fulham (92 as underdog) | 22.9% | 27.2% | ±9.1 |
| Augsburg (130 as underdog) | 22.7% | 26.9% | ±7.6 |
| Manchester United (59 as underdog) | 25.1% | 28.8% | ±11.6 |
This is the main caveat, and it applies to every chart here. A club sample of 40 to 150 matches leaves wide uncertainty, and several of these clubs changed managers or squads heavily during the window. The Villa that appears in these numbers is really more than one team, so a strong record over five seasons describes the past. It does not forecast the next match.
Section CBacking Aston Villa as underdog returned more than any other club
Win rate and profit are not the same thing, because the price you get matters as much as how often you win. At flat stakes, backing Aston Villa every time they were underdog returned +57.4%. Lens returned +31.2%, Augsburg 32.5% and Sassuolo 28.3%.
Brighton show why the two measures can come apart. They won slightly more often as underdog than Lazio did, yet Brighton returned +11.6% while Lazio returned +22.8%. Lazio's underdog wins tended to come at bigger prices, and that is where the return came from.
View the data: flat-stake return backing them as underdog
| Return | |
|---|---|
| Aston Villa | +57.4% |
| Lens | +31.2% |
| Brighton | +11.6% |
| Lazio | +22.8% |
| Sassuolo | +28.3% |
| Union Berlin | +8.1% |
| Brest | +5.8% |
| Fulham | −0.3% |
| Augsburg | +32.5% |
| Manchester United | +7.4% |
Fulham are the useful counterweight. They beat their priced chance on the dumbbell chart but roughly broke even at flat stakes. Outperforming the odds a little is not enough on its own once the bookmaker's margin is in the price.
Section DSassuolo, Aston Villa and Union Berlin produce the most upsets either way
The final chart combines both roles. It shows the share of each club's matches that ended with the underdog winning, whichever side that was. Sassuolo lead again. In 32.2% of their 152 matches the underdog won, which was 49 games, against 24.8% implied by the odds. Aston Villa recorded 30.0% of 190 against 24.9%, and Union Berlin 30.0% of 170 against 25.4%.
Sassuolo are the clearest example of a genuinely unpredictable side. They let favourites' prices down and also beat the odds as outsiders. For anyone building a model, a club like that pulls its outcomes towards the middle of the probability range, and I treat any confident price on them with caution.
View the data: share of matches ending in an upset either way
| Upset = underdog won; top 10 clubs with 76+ matches | |
|---|---|
| Sassuolo | 32.2% |
| Aston Villa | 30.0% |
| Union Berlin | 30.0% |
| Parma | 28.9% |
| Everton | 27.9% |
| Lorient | 27.8% |
| Reims | 27.8% |
| Augsburg | 27.6% |
| Rennes | 27.5% |
| Toulouse | 27.1% |
Set that against the league-wide figure of 20.9% and these clubs stand clearly apart. Because the market gets the overall upset rate about right, any edge sits at the club level rather than in backing underdogs as a general habit.
Club verdict
What this file means before you bet.
- Question short Sassuolo prices. Sassuolo lost 37.5% of games as favourite against a priced 27.3%. When they are made favourites, I want a clear reason before I trust the price.
- Respect Villa as underdog. Aston Villa won 39.2% of underdog matches against 24.3% priced, and returned +57.4% at flat stakes. Club samples are small, though, so treat this as a prompt to look closer rather than an automatic bet.
- Weigh sample size first. Chelsea's +4.0 gap over 157 matches as favourite is steadier evidence than a larger gap over 55. Read the match count before you read the gap.
Frequently asked
Which big-five club loses most often as favourite?
Sassuolo lost 37.5% of their 56 league matches as favourite, against 27.3% priced by the closing odds. That gap of +10.2 points was the largest in the study.
How often do underdogs win in the big five leagues?
Across 8,906 matches, the 1X2 underdog won 20.9% of games. The no-margin odds implied 22.8%, so the market priced underdogs fairly well overall.
Has backing Aston Villa as underdog been profitable?
Over the window, backing Aston Villa every time they were underdog returned +57.4% at flat stakes from 79 matches. The 95% range on their win rate is ±10.8 points, so the record is strong but uncertain.
I'm Olivia Bennett, Statistical Modelling Lead at BettingTips2. I design the probability frameworks that turn raw football data into the percentages you see attached to our predictions.
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