Do Teams Favored by AI Become More Favored Before Tip-Off?
Three AI models forecast win chances before games; we check whether they anticipated pre-game odds moves and compare their accuracy. Part 1 uses the new NBA season; Part 2 looks back at 2026 MLB forecasts already locked before games on aisportsinfo.com.
Study details
On this page
In plain words
What do we want to know?
We want to know three things: Are the win chances AI gives accurate? Does AI guess ahead of time which way the odds will change before tip-off? And is looking at “market odds + AI” together more accurate than looking at the market odds alone?
How do we study it?
Polymarket is a prediction platform where people buy and sell shares in game results. The price is between $0 and $1; a price of $0.60 roughly means the people trading think, as a group, that this side has about a 60% chance to win (the crowd’s view, not necessarily the true chance). For every NBA game, 6 hours before tip-off, we ask three large language models (Claude, GPT, Gemini) to each give a win chance for the home team. The AIs can’t go online; they only see the official schedule and scores, injury reports and player stats at that moment, and no odds at all. Every prediction is kept with its content and time and timestamped, so anyone can check whether it was changed later. We then compare it with the Polymarket odds at the same moment and the last odds before tip-off.
How do we compare AI with the market?
- 016 hours before: freeze inputs
Provide schedules, player data and injury reports, but no market odds or internet access.
- 02Three independent AI forecasts
Claude, GPT and Gemini each estimate the home team’s chance, without assuming which is best.
- 03Preserve forecasts and times
Record and timestamp forecasts so their timing and later changes can be checked.
- 04Evaluate after the season
Compare the odds at the time, the closing odds and game outcomes; evaluate the direction of odds separately from forecasting accuracy.
This is a study workflow, not an AI performance chart. No invented win rates or profit curves are shown before analysis.
Where are we now?
Automatic daily collection started on 2026/10/21. We will analyze only once, after the regular season ends (2027/4/11), so no one can peek midway or pick the results they like. There are no results yet.
Track record already public
Our other site, aisportsinfo.com, publishes three AI models’ pre-game MLB forecasts and checks them after each game. Through Oct 20 of the 2026 season, the three-model consensus picked 494 of 878 games correctly (56%)—Claude 57%, ChatGPT 56%, Gemini 54%—versus 53.8% for always picking the home team. These hit rates are already public, so they are not blind; what nobody has computed yet is how the AI views compare with Polymarket odds, which is what Part 2 answers.
What can’t we say yet?
The AIs only see the data we give them, so the results don’t show how AI would do when it can look things up online. The three AIs run on existing subscription plans; when usage limits run out, a few games will be missing, and any gaps will be recorded honestly. This study tests general AI models, not Mysports’ own prediction models.
Terms used on this page
- Polymarket
- A prediction platform where people buy and sell shares in game results. Prices run from $0 to $1 and roughly show the chance the traders think an outcome has — not necessarily the true chance. A price converts directly to odds: odds = 1 ÷ price.
- Large language model (AI)
- AI such as ChatGPT, Claude and Gemini that can read text and answer questions.
- Timestamped record
- Keeping the content and time of every prediction and timestamping it, so anyone can check that the prediction was made before the game and wasn’t changed afterwards.
- Closing odds
- The last odds recorded before the game starts; they usually reflect the most news.
Background and why it matters
AI predictions are more and more common, but few people have tested “can AI see the direction before the market does” using predictions recorded and timestamped in advance. The results tell our models whether AI opinions are worth using as an extra signal.
Research questions
No results yet — here are the research questions and current progress.
- Are the win chances AI gives accurate?
- Does AI guess ahead of time which way the odds move before tip-off?
- Is “market odds + AI” more accurate than looking at the market alone?
Latest progress
Latest：Part 1 (NBA) is collecting daily; Part 2 (2026 MLB look-back) plan finalized and timestamped
Collecting：Win chances from three AIs, 6 hours before each game of the 2026-27 NBA regular season (recorded and timestamped)
Next step：Run Part 2 analysis by 2026/11/30; analyze Part 1 after the regular season ends in April 2027
Study timeline
- Novelty checked; plan finalized and timestamped2026-10-21
- Part 2 (2026 MLB look-back): data audited, plan finalized and timestamped2026-10-21
- Collecting AI predictions every day, 6 hours before each game (until 2027/4/11)In progress2026-10-21
- Part 2 analysis, external code review and publication (by 2027/1/31)
- One analysis after the regular season ends, external code review, publishing results (by 2027/5/15 at the latest)
Methods
Hypotheses
- H1AI’s win chances will be less accurate than the market’s at the same momentPending
- H2The gap between AI and the market probably can’t predict which way the odds go laterPending
- H3“Market odds + AI” is probably not more accurate than looking at the market alonePending
Method summary
- The instructions given to the AI and the AI versions are written into the plan in advance, with a “digital fingerprint” of the files kept, so they can’t be secretly changed later. The AI runs in an empty folder and can’t go online or use tools; if any market-related word appears in the data, it isn’t sent.
- We analyze only once, after the regular season ends; if fewer than 600 games are usable, we only describe the results and draw no conclusions.
- Part 2: 2026 MLB forecasts already locked before games and pushed to GitHub by aisportsinfo.com (about 829 regular-season games), compared with Polymarket odds at the same moment and at close. We checked that the AI inputs contained no odds and almost no web access, but they did include ESPN’s win probabilities, so conclusions describe AI performance after seeing ESPN’s numbers.
Data and limitations
Data we use
- Pre-game win chances from three large language models (6 hours before each game, recorded and timestamped)
- Polymarket odds for single NBA games (shared with R1)
- Official NBA schedule, injury reports and player stats
- aisportsinfo.com: three AI models’ 2026 MLB pre-game forecasts and record (Part 2; same team as Mysports)
Limitations
- The AI can’t go online, so the results don’t show how AI with internet access would do.
- We use existing subscription plans, so there will be gaps when the usage limits run out.
- Part 2 is a look-back study using data our own site produced; Claude’s logs before 9/20 were deleted by the system, so a version excluding those forecasts will be published alongside.
Update log
Version history
- p2-v1.02026-10-21
Part 2 plan finalized and timestamped (T0 = 2026-10-21 08:23 UTC) after two external reviews
- v1.02026-10-21
Study plan finalized and timestamped (T0 = 2026-10-21 05:22 UTC); collection started
Study record
b35be5c62216364b0cf9ab6e454ff91b09f5583cc90c200e6b84332d0c7e99c2b186f633f44d48af9ea11e933298ba28b8db7a8d522b406c3de79ffffb42f464014c0f9debbd17614cc84daec96315175d3ce5daa537d78e4029fc6a68c4da547d881bc57a6e3802489783284c74dcbf5c59a7f50f2cc0a964ec0824ea1eb862This page is a research log for reference only and is not betting advice or a guarantee of profit.