Mindlessly following Polymarket's pre-game win probability trades for NBA, can you make a guaranteed profit?

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Trading NBA games on Polymarket, perhaps like many others, you’ve experienced this: before the game, one team’s win probability is clearly higher than the opponent’s, but in the fourth quarter, they suddenly collapse and get swept away (like the recent Hornets and Heat—those trades almost made me question my life).

Since everyone says Polymarket is a “truth machine,” does that mean if I blindly buy the team with the higher pre-game win probability, I can easily make money?

To verify this hypothesis, I backtested 1,096 regular-season NBA games from the 2025-26 season. The data reveals that—

Blindly following the market won’t make you rich, but it also won’t lose much; pre-game probabilities are already fully priced in.

Blindly buying according to the market, guaranteed profit

The backtest strategy used is very simple:

Use the average pre-game probability over the first 3 minutes as the baseline

Trade $100 per game

Always buy the team with the higher “win probability”

Results:

Total expenditure was $109,600, total returns were $107,545.20, resulting in a loss of $2,054

ROI was -1.87%

This indicates that Polymarket’s prices are already quite efficient; the market has fully priced in the teams’ win probabilities, leaving no “arbitrage” opportunities.

The ROI difference may come from transaction costs, emotional premiums, and other factors; even blindly buying or going against the market can yield a 1.87% return.

The true value: teams cannot be generalized

The above backtest was conducted on a total of 1,000 games. I also broke down the data from multiple angles, trying to find parts that can break the market’s gravitational pull:

By week: Random walk

By probability: Still a random walk. Betting on pre-game win probabilities of 50%, 60%, versus 70%, 80% shows no difference in returns

By team: Significant differences emerge here

Some teams truly live up to market trust—

As long as the market believes they will win, they are more likely to actually win.

POR (Trail Blazers): ROI 19%

PHI (76ers): ROI 14%

SAS (Spurs): ROI 12%

LAL (Lakers): ROI 11%

CHA (Hornets): ROI 9%

Why do these teams show such differences? Since I previously had limited knowledge of NBA teams, I had a hypothesis:

Are they the strongest or weakest teams, thus having high consistency in expectations?

But after verification, that’s not the case. Except for SAS (Spurs), the other four teams are only ranked slightly above the middle.

What about the best-performing teams? In fact, the market has already fully priced them in; blindly following them yields an average ROI of only 2.16%, with no inflation in pre-game win odds.

DET (Pistons): ROI 1%

BOS (Celtics): ROI 4%

NYK (Knicks): ROI 3%

OKC (Thunder): ROI -2%

DEN (Nuggets): ROI -5%

And the weakest teams?

Here, the divergence is extreme. These teams rarely get market pressure to win, for example, the Nets (BKN) with only 7 wins over 50%, winning 5, ROI as high as 21%; while the Pacers (IND) with only 8 wins over 50%, winning 4, ROI is -20%. The sample size is too small to serve as a trading reference.

In other words, theoretically (just theory!), POR (Trail Blazers), PHI (76ers), SAS (Spurs), LAL (Lakers), CHA (Hornets) are the ranges you can follow based on current data.