StaChesstics Presents: A Data-Driven Retrospective on Prague International Chess

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At StaChesstics, we were proud to be the official partner of the event. Some of our team memebers attended the tournament and enjoyed every moment in its vibrant atmosphere. The Festival not only organized multiple tournaments over two exciting weeks, bringing together hundreds of chess players, but also created an environment that was fun and engaging for everyone involved. The organizers worked like a close-knit family, and their chemistry is a big reason why such a strong lineup of elite players could be assembled.
StaChesstics team members Araghi and Atefeh Khosravi with PICF director Petr Boleslav.
StaChesstics team members Araghi and Atefeh Khosravi with PICF director Petr Boleslav.
In this report, we break down our AI-driven predictions and the actual outcomes of the tournament. We know that sometimes our numbers can seem vague or hard to explain. Our goal here is to shed light on those figures and show you how, over many simulated tournaments, they represent long-term trends and real possibilities. Join us as we explore the highs, lows, and dramatic twists of this incredible chess event.

Stage 1: Predicting the Unpredictable – The Power of Chess Probabilities

The Masters Lineup

The Prague International Chess Festival’s Masters stage brought together 10 elite players, with an average rating slightly above 2700. Before the tournament began, we used AI-driven analysis to assess each player's chances, considering factors like ratings, opponents, and assigned colors. These predictions don’t attempt to “guess the winner” but instead answer one question: If we ran this tournament 100 times, how often would each player win?
Prague International Chess Festival Masters Lineup
Photo by: Prague International Chess Festival

The Tournament Winning Chances Before Round 1

“Sole Winner” refers to finishing first outright, while “Playoff” means tying for first and then finishing in the top two based on tie-break rules.

Think of these numbers like rolling dice:

• Rolling two dice gives a 2.7% chance of getting double sixes—rare, but possible.
• The chance of rolling at least one "2" is 30.5%—much more likely.
• If we roll double six, it doesn’t mean our predictions were wrong—it’s just one possible outcome.

Similarly, our predictions don’t claim that “Vincent Keymer will win”. Instead, they indicate that 'In 100 parallel “Prague International Chess Festival Masters 2025” tournaments (think Rick and Morty style), he wins outright in 8, reaches the playoffs in 7–8, and finishes in the top 3 in 36. Even if he underperforms in this particular tournament, the math remains correct. It reflects long-term trends.

Why This Analysis Matters

Chess is inherently unpredictable. A single mistake, a moment of brilliance, or even the advantage of playing white can shift the odds. Our predictions:

• Highlight Underdogs vs. Favorites: For instance, Praggnanandhaa's 14.45% chance contrasts with Gurel's 0.35%, indicating differing expectations.
• Show Volatility: Early wins or losses can dramatically alter probabilities. For example, Vincent Keymer's five decisive results in five rounds defied expectations and reshaped the tournament.
• Add Drama: Numbers transform abstract battles into measurable stakes, enhancing the spectator experience.

Understanding these probabilities offers deeper insight into the dynamics of high-level chess competitions, where every move can significantly impact a player's tournament trajectory.

Stage 2: Round 5 – The Berlin Draw That Shaped the Tournament

After four rounds, GM Aravindh Chithambaram VR and GM Praggnanandhaa R both had 3 points, leading the field by a full point. Their head-to-head match in Round 5 was a turning point.
Round 5 key match
Photo by: Prague International Chess Festival

Standings Before Round 5

In this crucial game, Praggnanandhaa played the Spanish Opening and allowed the Berlin Defense, a line known for leading to draws. On move 15, Praggnanandhaa played the rare move Qe3. Soon after, the position fizzled out into a symmetrical endgame where White was very safe, making a draw the most likely outcome.
Round 5 key match
Photo by: Petr Vrabec
Our numbers showed that in the event of a blitz playoff between the leaders, Praggnanandhaa would have a 63% chance of winning. However, a win in this game would have boosted his title odds to 66.7%, while a loss would have slashed them to 3.8%. Ultimately, the draw reduced his winning chances from 48% (if he had pushed for a win) to 40.3%—a drop of roughly 7–9%.
This cautious choice helped him avoid a loss that might have ended his title hopes. While some might argue that playing aggressively could have been better, taking a safe draw was a logical decision at the time.

Stage 3: The Final Sprint – Pressure, Predictions, and Must-Win Moments

After 6 rounds, Aravindh and Praggnanandhaa were still a full point ahead of four other players, who each had 3 points. This was a key moment in the tournament.

Standings After Round 6

We expected both Aravindh and Praggnanandhaa to finish with about 5.5 to 6 points. It was highly likely that one of them would reach 6 points—which indeed happened. This meant that with only three rounds left, a player with 3 points could no longer afford to drop points if they hoped to keep their playoff chances alive.
For them, every game became a must-win, even though it seemed like just a one-point deficit. The round turned out to be exciting, with three out of five decisive games. But none of the four trailing players could secure a win, meaning that almost certainly, the winner would be either Aravindh or Praggnanandhaa.
Aravindh & Praggnanandhaa.
Photo by: Petr Vrabec

Stage 4: Data vs. Gut Feeling – How Numbers Cut Through the Noise

The Human Bias Trap

We all love a good story. People often talk about “momentum,” “experience,” or “killer instinct” when predicting chess tournament winners. But how much of that is real, and how much is just human bias?
For instance, during the 2024 Candidates Tournament, hardly anyone predicted Gukesh’s victory—even though the data quietly hinted at his rise.
Similarly, critics questioned why our model favored GM Aravindh early on. The answer is simple: data ignores narratives. It focuses purely on patterns and probabilities.

Standings After Round 7: The Final Stretch

Breaking Down the Numbers

• The 0.5-Point Illusion: A small 0.5-point gap may seem minor, but at this level, it’s massive. Even though Praggnanandhaa was only half a point behind, his direct win probability was just 6.3%—because catching up in only two rounds is incredibly difficult unless his rival falters.
• The 75.2% Statistical chance: Aravindh’s dominance wasn’t just about scoring points—it was about building an unstoppable lead. His expected score of 6.2 points was perfectly aligned with his strong performance. But even with a 75% chance to win, nothing was 100% guaranteed. as his 18.1% playoff risk showed.
• Interestingly, at this stage, Praggnanandhaa had nearly a 29% chance of finishing outside the top 3. While that seemed unthinkable at the time, it did happen.

Ali Araghi
Araghi, Founder of StaChesstics, made the ceremonial first move on GM Aravindh Chithambaram vs GM David Navara. Photo by: Shahid Ahmed, Chessbase India

The Final Round – Chaos, Tie-Breaks, and a Dramatic Finish

The Last Stand – Pre-Game Probabilities

With one round to go, everything was still up in the air. Our model had GM Aravindh as the clear favorite, with an 82.6% chance to win outright. GM Praggnanandhaa, on the other hand, had just a 1.5% chance of taking sole first but a 15.6% shot at forcing a playoff. Meanwhile, GM Wei Yi was fighting for third place, and despite being in sixth at the time, GM Anish Giri had a surprising 19% chance to finish second—but oddly, only a 3.4% chance of ending up third! We’ll get into why soon (spoiler: tie-break rules can get weird).
Here’s how things stood before the final round:
Standings before the final round
StaChesstics' Live Standings & Predictions before the final round

The Tie-Break Tango

As key games wrapped up in draws—David Navara vs. Shankland and Aravindh vs. Ediz Gurel—Wei Yi’s slim 0.3% chance of forcing a playoff vanished. Meanwhile, Praggnanandhaa found himself in a tough spot against GM Anish Giri, with his position looking far from promising.
At this stage, our live standings and prediction table showed:

With Anish Giri defeating Praggnanandhaa, he pulled off an impressive comeback. Just two rounds earlier, he was sitting in 9th place with only 3 points. But with back-to-back wins, he climbed to 5 points, securing second place after Wei Yi’s game ended in a draw.
GM Anish Giri
Photo by: Petr Vrabec
Now, only one game remained.
Live Standings & Predictions during the final rounds
StaChesstics' Live Standings & Predictions during the final round

Tie-Break Drama at the Prague International Chess Festival

In chess, tie-break rules can completely shift final standings. At the Prague International Chess Festival, if players finish with the same points, the rankings are determined by head-to-head results (H2H) and Sonneborn-Berger (SB) scores, before considering the number of games played with the black pieces.
For example:

• Anish Giri’s win over Praggnanandhaa propelled him from 6th place to a strong shot at second.
• Wei Yi’s high SB score gave him an 81.5% chance of finishing third.

But here’s where things got interesting: the final ongoing game (Vincent Keymer vs. Nguyen) didn’t involve any top-three contenders. However, its result could determine whether Wei Yi or Praggnanandhaa secured third place. How?

• If Vincent won, he would join the 5-point group. The head-to-head standings among the tied players would be:
  • Anish: 2 points
  • Praggnanandhaa/Vincent: 1.5 points
  • Wei Yi: 1 point

Since Praggnanandhaa had the better Sonneborn-Berger score than Vincent, he would take third place.

• However, if Vincent didn’t win, the H2H table would be:
  • Anish: 1.5 points
  • Wei Yi: 1 point each
  • Praggnanandhaa: 0.5 point

In this case, Wei Yi’s stronger SB score would push him ahead, leaving Praggnanandhaa in fourth.
This explains why Wei Yi’s probability of finishing third wasn’t 100%—because there was an 18.5% chance that Vincent could win and shift the standings in Praggnanandhaa’s favor.
Unfortunately for Praggnanandhaa, that didn’t happen. Vincent didn’t win, Wei Yi secured third place, and despite a strong tournament, Praggnanandhaa had to settle for fourth.
Aravindh won the 7th Prague International Chess Festival, Masters
Photo by: Prague International Chess Festival

Key Deviations: Predictions vs. Reality

To wrap things up, let’s compare our pre-tournament expectations with the final results. At the start, we provided an expected score for each player based on our AI model, different from the traditional Elo expected score.
The table below shows how each player performed relative to these expectations. But again, this isn’t about being "right" or "wrong." These results reflect this tournament’s specific outcomes. If we ran a million parallel versions of the event, the expected scores would represent the players’ long-term averages.

Conclusion

At the Prague International Chess Festival 2025, our AI predictions provided a detailed roadmap of long-term trends, yet the decisions on the board ultimately wrote the final story. Early forecasts revealed a spectrum of possibilities, while critical moments—such as the Berlin draw in Round 5, the intense final sprint, and dramatic tie-breaks—demonstrated how every half-point and each decision could change a player's fate. GM Aravindh’s steady performance crowned him champion, GM Anish Giri’s bold comeback secured him second place, and the tie-break rules ultimately pushed GM Praggnanandhaa to fourth.
In elite chess, while data offers valuable insights, it is the human spirit and split-second decisions under pressure that transform predictions into history.

You can get updated odds and more stats on our website https://stachesstics.com. If you want more stats or have any thoughts, let us know! We're here to listen. Your feedback helps us get better and give you what you need. Thanks for being with us