On May 15th, the Tennis algorithm hit a losing streak. In this article, we’ll explore what might be causing this and review each tennis tournament to see if it’s normal variance or something else.
TLDR: Between January 1, 2024, and June 17, 2025, the system remains profitable in units, but the euro profit is below expectations.
Is it just variance, a one-off blip, or something more? As we’ve discussed on Discord, the system still bets with positive EV as it always has. It’s validated by thousands of bets over 9 years, simulations, and the real results of many users. Negative weeks can happen, and longer losing spells can emerge even with a proven +EV system.
Looking closely, around pick #17,000 (week 18 of 2025), the profit line in euros dips below the EV line. Simply put, when the blue line is above the green, luck favors us. When it’s below, it does not.
Weeks have passed where EV kept climbing, but real-world profit didn’t. This isn’t our first dip, nor the worst in terms of profit lost. To understand why this happens—and why it doesn’t mean the system is broken—we revisit the foundation of WinnerOdds: betting with positive expected value (EV+).
The expected value is calculated by the formula:
EV = Bet Size * (Bet Odds * True Odds – 1).
Due to recent disappointing results, if WinnerOdds’ minimum odds aren’t precise, we need to estimate true probabilities another way. By CLV (Closing Line Value) theory, the true probability is the one implied by the bet’s closing odds.
Using those, strip the bookmaker’s margin:
Margin = (1 / Closing Odds Player 1) + (1 / Closing Odds Player 2) − 1.
True Closing Odds = 2 * Closing Odds / (2 − Margin * Closing Odds).
“True Probability” = 1 / True Closing Odds.
As @12xpert explains in his paper: https://www.football-data.co.uk/The_Wisdom_of_the_Crowd_updated.pdf, for average odds placed, divide potential profit by total staked, plus one:
Average Odds Placed = (Potential Profit / Total Staked) + 1.
This factors in odds from opening until they cross WinnerOdds’ minimum odds. Compute each bet’s expected value:
EV = Total Staked * (Average Odds Placed / True Odds − 1).
The EV+ hasn’t vanished, but profit hit a wall. When losing weeks pile up, doubts arise. But the data shows the system still works. It identifies EV+ bets consistently.
When results are in units (Profit Units / EV Units), the system is still functional. The blue curve (actual units won) stays above the EV line, often widening the gap. The algorithm works—sometimes outperforming expectations.
Poor results are likely not from the algorithm but from lower average odds, smaller bankrolls, and betting limits.
After bet 18,000, Bet365 reduced liquidity in many regions, impacting stake per bet and damaging the overall EV curve. The system still generates +EV bets, but stakes are smaller.
Looking at each tournament reveals more details.
ATP: The men’s ATP Tour is the most-followed. The system profited above the EV+ line, but in euros, a sharp decline occurred between bets 1,000 and 1,500. The maximum drawdown was roughly –€140,000.
WTA: The system consistently stayed above EV in units, spiking in the last section. In euros, it shows positive variance—initial returns exceeded EV. Variance impacts results, explaining daily user variations.
CHALLENGER: The season mirrored WTA’s, nearly €500,000 in profit, then plummeted. In units, it was a mild setback, but in euros, the impact was harsh, erasing prior gains.
ITF MEN: This circuit was linear and stable, ticking along above EV with no shocks. In euros, it earned steadily, stabilizing after bet 3,000.
ITF WOMEN: This followed a steady climb, aligning with EV. In euros, the blue curve lagged but improved after bet 2,000, marking a recovery.
Reasons behind these fluctuations:
1. Lower liquidity at Bet365 Spain and others.
2. Pinnacle isn’t affected by WinnerOdds.
3. Stake caps at bookmakers.
4. Possible initial positive variance.
The system still creates value, and the average user wins.
Monte-Carlo simulations often help address whether it’s luck or system failure. By simulating bets, stakes, and EV thousands of times, different outcomes emerge but with the same EV.
Each colored line is a potential reality, impacted by chance.
- SCCG Management. The Gambling Industry’s Global Connector. Access Here.
- Source: SCCGManagement.com