To athletes, momentum is a revered but shapeless concept, an aspiration to an undefined state of being whose existence is not doubted. To question it is to ask whether the sky is blue.
“It’s a real thing,” said Red Sox shortstop Trevor Story. “And it can obviously flip a season on its head.”
Story, of course, was referring to a 2026 Red Sox campaign that has featured an almost unprecedented pairing of extremes.
For nearly half a season, the team — and particularly the lineup — saw failure snowball, leading the team down a 32-46 chasm. With alarming frequency, rallies went nowhere, with the team treating opportunities with men in scoring position like radioactive waste.
And then, as if at the snap of a hypnotist’s fingers, the team transformed into one where all the parts aligned perfectly, where a double followed by a well-placed bunt might be followed by a walk, then a hit, then another.
At-bat to at-bat, game to game, win to win, the Sox rode upon a wave that kept surging. Since June 25, the Sox have won 32 of 38 games, just the 20th instance since 1901 of a team winning that many games in that short a period of time.
To Sox interim manager Chad Tracy, both stretches served as testament to the power of Mighty Mo(mentum).
“What you saw the first few months, where everybody was struggling and just felt like nothing was going right, and when you see things going on with your teammates, it’s not good. It’s like, ‘Man, this guy must be throwing it good, [because] nothing’s happening,’ ” said Tracy. “And now you get to a period where you’re asked to bunt, you execute, get in a sac fly situation, you get it done. We need a double. Boom, it happens. Everybody feeds off that. I think baseball more than anything is probably a sport that feeds off of the other people around you.”
The feeling of momentum — perhaps a flow state for an individual player, or a collective confidence from a team borne by all the members of the roster recognizing their specific roles and abilities and playing within them — is undeniable. But can it be quantified?
“Probably not,” said Story. “You can just feel it. It’s obviously not a tangible thing you can touch, but it’s something that you can feel, and we’re feeling it every night here at Fenway.”
But the inability to quantify momentum has made it a disputed notion for decades. Scholars such as renowned behavioral economist Amos Tversky have studied concepts such as “the hot hand” in basketball and concluded that it doesn’t exist, instead deeming the notion of such “in-game momentum” as a misinterpretation of random sequences of events. Similar findings have occurred at the team level.
Of course, something need not be quantified for it to exist. When nearly everyone who has spent a lifetime in sports swears by the idea that there’s carryover in the physical and mental state from one moment or game to the next, there’s probably something to the concept.
“Just because a bunch of math types can’t figure out how to quantify something doesn’t mean it’s not real,” said Tom Tippett, a Red Sox analyst from 2003-16. “It’s a game played by humans, right? If people approach their craft in a different way because they believe something’s true, that’s probably going to affect their performance.”
But what if there were a way to quantify momentum? Perhaps there is.
As it turns out, baseball streaks tend to be somewhat self-sustaining. A Globe analysis of Retrosheet data that includes the outcome of every MLB game from 1901 through 2025 revealed a striking pattern: The longer a winning streak lasts, the higher a team’s winning percentage in the next game.
In a vacuum, one might expect the outcome of every game to be close to a coin flip. Regardless of whether a team has claimed victories in two or 10 straight games, the likelihood of a win in the next game should be unaffected.
In evident confirmation of that notion, teams amidst a “one-game winning streak” or “one-game losing streak” (yes, such terms are oxymorons) have about a .500 winning percentage for the subsequent game.
But things get interesting once teams repeat outcomes. Clubs with a two-game winning streak have a .516 winning percentage in the following game, a .535 winning percentage after winning three straight, and a .551 winning percentage after winning five straight.
The reverse occurs during losing streaks. Clubs that have dropped two straight contests have a .486 winning percentage in the next one, a .475 winning percentage after three straight losses, and a .451 winning percentage after dropping four consecutive contests. The consistency of the pattern — winning percentages going up as winning streaks progress, and going down as losing streaks lengthen — is striking and largely holds up across eras in baseball history.
Streaks become, at least by winning percentage, more likely to remain intact the longer that they continue. One could view the trend as evidence of the power of momentum, statistical evidence that teams are indeed capable of running downhill or uphill together.
There are major confounding factors to note with the pattern — particularly when it comes to the quality of teams and their competition. A giant gambling industry, in fact, depends on the idea that win probability isn’t 50-50 for all teams.
Typically, a long winning streak is a signal of a team’s strength, meaning that clubs reeling off 10 or 15 straight wins generally will be very good — and would thus have an expected winning percentage exceeding .500. Perhaps, then, the rising winning percentage within streaks is not an indication of momentum but instead of a team’s actual ability.
And then there are elements that defy predictable patterns: Randomness and luck. It is not merely momentum — a positive feedback loop of one team’s performances — that sustains winning streaks, but also timely misplays and mislocated pitches by an opponent.
The Red Sox’ winning streak in July likely should have expired after eight games, but with the Sox trailing, 2-0, in the ninth inning on the final game before the All-Star break, Mets shortstop Francisco Lindor botched what should have been a game-ending double play. The Sox tied the score, then won in extras.
A moment like that helps explain why a winning streak like the 15-gamer that vaulted the Sox this year from last place into playoff contention can assume magical dimensions. It relies on many components that can be explained and quantified and some that can’t. Somewhere in the latter category, players insist, lies the power of momentum ― a phenomenon that they care only about feeling, and not counting.
Julian Benbow of the Globe staff contributed to this story.
Alex Speier can be reached at alex.speier@globe.com. Follow him @alexspeier.