Why 25-0 Runs Die Around Fights 13 to 20 (It Is Not Mostly Cardio)
2,500 drafted builds × 40 careers, plus 100,000 controlled careers · seed 303
By Haaris A · Published October 13, 2026 · 8 min read · How we work
The short version
The wall is at fights 10 to 15, and the cardio penalty arrives just after it. Players blame the late career because that is where they remember losing, but the data say otherwise. Across 2,500 realistic drafted builds, 78.2% of careers took their first loss before fight 16. Only 12.3% took it in fights 16 to 25, and 9.4% went the whole way. The streak hazard, meaning the chance of losing a given fight when you are still unbeaten, peaks at fight 13 for realistic builds.
So where does the common wisdom come from? It is half right. The matchmaking target does ramp up into a plateau that hurts from fight 13 to 20, and the cardio penalty does start after fight 15 and does compound. But cardio is the smaller of the two forces, and the one you fully control. A player who drafts cardio at 94 or better barely notices the penalty. A player who ends up at 80 pays for it every fight from 16 to 25.
What the simulator does to an unbeaten career
Opponent difficulty is driven by a target rating. It starts at 66 for fight one and climbs about 1.8 points per fight, since the base curve rises with the fight number and every win adds another 0.8. At four straight wins there is a hot-streak spike of four points, which is why fight five jumps from 71.4 to 77.2. The target reaches its ceiling of 92 at fight 14 and then stays there for the rest of the career: 86.2 at fight 10, 89.8 at fight 12, 91.6 at fight 13. Title fights are pinned at 88 regardless.
Opponents are then drawn from the division within six points of that target, and nobody is reused except your designated rival. In our middleweight test, a flawless 95 build faced opponents averaging 75 in fight one and 84 by fight ten, levelling off at 86 from the mid-teens. After fight 19 the average actually slips, to 84.3 by fight 25, because the best names in the division have already been used. The late schedule is the same as the schedule at fights 13 to 15, not harder.
That is the first reason the zone from 13 to 20 is where runs end: the ramp has just finished, every opponent is now at or near the top of the pool, and you still have a dozen fights to survive.
Why division depth matters late
The second rule is about who is left. Outside your designated rival, the simulator never reuses an opponent in a single career: every other name is used once. The rival can appear up to three times in a career, at least four fights apart, and takes the title defences when available. So a long unbeaten run needs a division with a deep bench of fighters rated near the target, because title fights aim at 88 and the ceiling is 92. When the pool near the target runs out, the simulator widens its search and takes the closest names it has left.
| Division | Entries | Rated 88+ | Rated 90+ | Best |
|---|---|---|---|---|
| Lightweight | 46 | 11 | 4 | 92 |
| Heavyweight | 40 | 8 | 4 | 94 |
| Welterweight | 48 | 7 | 4 | 93 |
| Light Heavyweight | 40 | 6 | 2 | 94 |
| Featherweight | 38 | 6 | 3 | 92 |
| Middleweight | 44 | 5 | 0 | 89 |
| Bantamweight | 36 | 5 | 0 | 88 |
| Flyweight | 39 | 2 | 1 | 90 |
Rating = the simulator's overall for an opponent: the mean of the fighter's eight attributes in their best edition, rounded. This is the number matchmaking compares with the target, so it is the one that matters here, not the card Overall.
Lightweight carries the deepest title-ready bench, 11 of its 46 entries at 88 or higher, so a long career there keeps meeting fresh late-game opponents. Flyweight has 2 out of 39. A run there is still possible, but expect the rival and the widened search to fill the late schedule. That is why the plateau in the next sections looks the way it does: the hardest fights are the ones the pool can actually supply.
The cardio penalty, in exact numbers
From fight 16 on, the simulator subtracts a penalty from your win rating equal to the shortfall in cardio, times the number of fights past 15, times 0.8. Each rating point is worth four percentage points of win probability, so here is what that looks like.
| Cardio | Fight 16 | Fight 18 | Fight 20 | Fight 22 | Fight 25 |
|---|---|---|---|---|---|
| 60 | −0.32 | −0.96 | −1.60 | −2.24 | −3.20 |
| 70 | −0.24 | −0.72 | −1.20 | −1.68 | −2.40 |
| 80 | −0.16 | −0.48 | −0.80 | −1.12 | −1.60 |
| 90 | −0.08 | −0.24 | −0.40 | −0.56 | −0.80 |
| 99 | −0.01 | −0.02 | −0.04 | −0.06 | −0.08 |
Rating points removed from the build's win rating. Multiply by four for the loss in win probability, in percentage points.
A 99 in cardio loses nothing worth measuring: 0.08 points at fight 25, about a third of a percentage point. A 90 loses 0.8 points at fight 25, or 3.2 points of win probability. A 60 loses 3.2 rating points at fight 25, which is nearly 13 points off every win chance. The penalty is linear in the shortfall and linear in the fights, so a bad gas tank is manageable at fight 16 and a serious problem by fight 22.
A controlled experiment
To isolate cardio we built five fighters that are identical in every attribute, all 92, except cardio, which we set to 99, 90, 80, 70 and 60. Each ran 20,000 careers through middleweight. The chart shows the hazard: the chance of losing at that fight given a flawless record to that point.
Even the cardio-99 fighter faces a hazard near 20% from fight 13 to fight 19. That is the matchmaking plateau, and it is the reason fights 13 to 20 are brutal for every build. The cardio-80 fighter faces about 27 to 30% across the same stretch, and the cardio-60 fighter close to 40% for most of it. Separating the two effects is straightforward:
| Cardio | Build average | Loss rate, fights 1–15 | Fights 16–20 | Fights 21–25 | Unbeaten after 15 | Finish 25-0 |
|---|---|---|---|---|---|---|
| 99 | 92.88 | 9.76% | 18.34% | 14.5% | 17.19% | 2.84% |
| 90 | 91.75 | 11.53% | 23.37% | 21.16% | 10.96% | 1% |
| 80 | 90.5 | 13.71% | 28.52% | 28.98% | 6.7% | 0.26% |
| 70 | 89.25 | 16.16% | 34.65% | 36.78% | 3.64% | 0.09% |
| 60 | 88 | 18.85% | 39.96% | 45.06% | 1.62% | 0.02% |
Dropping cardio from 99 to 80 raises the loss rate in the early fights by a factor of 1.4, from 9.76% to 13.71%. That is the lower average at work, since cardio counts in the plain mean like every other attribute. In fights 21 to 25 the same drop raises the loss rate by a factor of 2.0, from 14.5% to 28.98%. The gap between those two multipliers is the penalty. Put plainly, weak cardio hurts before the penalty even exists, and then hurts roughly twice as much once it does. The practical result: the chance of reaching fight 16 unbeaten falls from 17.19% to 6.7%, and the 25-0 rate falls from 2.84% to 0.26%.
What realistic drafts look like
The controlled test is extreme on purpose. In real drafts, cardio is the easiest attribute to find: a typical board of five fighters offers a best cardio of 91.7, and 72.1% of spins show a 90 or better. Of the 2,500 builds drafted by a bot that takes the biggest surplus each round, only 85 (3.4%) ended with cardio under 88. They lost 16.29% of fights 16 to 20, against 11.63% for the 1,949 builds with cardio at 94 or higher, and expected 2.97 losses over a career against 2.29.
That is a real effect, but it is about two-thirds of a loss per career at its worst, set against the fact that the overall odds of losing at least once are already above 90%. Weak cardio shortens a streak. It does not create the wall. Nobody who drafts Merab Dvalishvili’s or Colby Covington’s 99, or Frankie Edgar’s 98, needs to think about the penalty at all, and an old-school pick like Clay Guida’s 96 puts the cost of the penalty at under half a rating point by fight 25.
How to plan around it
Treat cardio as a floor, not a goal. The bar is about 94. In the controlled test, a 90 instead of a 99 cost 5.0 percentage points of loss rate across fights 16 to 20 (23.37% against 18.34%), part of it the lower average. Above 95 the return is negligible. Fill the slot with the first 94-plus you see rather than leaving it for the last round.
Durability counts like any other attribute. It goes into the same plain average, so a point of durability adds exactly as much win probability as a point of boxing or wrestling. What it adds beyond that is the shape of a loss: when you do lose, a low durability makes a knockout the likelier result.
Spend the rest of your attention on Fight IQ. The streak is decided in the thirteen fights from 13 to 25, which are all fought at nearly constant difficulty, so every point of rating you add is a flat reduction in a hazard sitting near 20%. A point of Fight IQ adds 0.205 rating points across a career, against 0.143 for cardio and 0.125 for every other attribute, which makes it the best use of a pick.
Take the belt early. Title defences against your rival average a softer opponent than ordinary late fights, which is a measurable counterweight to the plateau. The worked example in our annotated 25-0 run shows it happening, with three defences in a row against the same 80-rated challenger.
Expect to lose. A flat-92 build with cardio 99 finishes 25-0 2.84% of the time in middleweight. That is not a failure of the build; it is what 25 fights at 90-plus difficulty looks like. The goal is to push the first loss as late as possible, and to be in the division where it takes the longest.