Sal Stewart Leads MLB in RBIs but His Odds Have Fallen 11 Points

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Sal Stewart Leads MLB With 105 RBIs, So Why Are His Chances Dropping?

Sal Stewart of the Cincinnati Reds leads Major League Baseball with 105 RBIs in the Pro Baseball RBIs Leader prediction market as of September 4, 2026, with roughly three weeks left in the regular season. He is the first rookie to reach 100 RBIs since Pete Alonso in 2019. By any conventional measure, he should be tightening his grip on the RBI crown, not loosening it.

Yet the prediction market tells a different story. Stewart's implied probability has fallen from 65% to 54% over the past three days, an 11-point drop that briefly touched a period low of 52%. Kalshi prices him at 57%; Polymarket sits lower at 52%. That spread suggests both platforms are independently repricing the same risk, not reacting to noise on a single venue.

The drop is counterintuitive on the surface. Stewart hasn't slumped. He hit .304 with eight home runs and 21 RBIs in August, riding a second-half surge that produced an .859 OPS, 12 home runs, and 40 RBIs in 189 plate appearances since the All-Star break. The 11-point move requires an explanation rooted in something other than Stewart's own performance.

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Yordan Alvarez's Triple Crown Push Is the Real Competitive Threat

The explanation sits in Houston. The Associated Press reported on September 3 that Yordan Alvarez is actively pursuing a Triple Crown, meaning he is contending simultaneously for the batting average, home run, and RBI titles. A player chasing all three crowns draws enormous lineup protection. Pitchers cannot pitch around him without conceding damage elsewhere in the order. That dynamic inflates RBI opportunities at exactly the moment the season compresses.

This creates a two-front problem for Stewart's market position. First, Alvarez is a direct competitor in the RBI race, presumably within striking distance of 105 (the AP would not frame a Triple Crown narrative around a player trailing by 20). Second, the Triple Crown storyline generates its own market attention, pulling capital toward Alvarez contracts on both Kalshi and Polymarket. Bettors searching for Alvarez Triple Crown exposure are simultaneously repricing the RBI race. The 11-point drop in Stewart's probability does not require a Stewart injury or slump. It requires only a credible challenger gaining narrative momentum.

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The RBI Math: Can Alvarez Actually Catch Stewart in Three Weeks?

The market resolves on September 28, leaving approximately 18 to 21 games for each team. Stewart's pace since the All-Star break translates to roughly 1.5 RBIs per game started. If he maintains that rate over 20 remaining games, he projects to finish near 135 RBIs, a total that would be the highest rookie mark in decades.

But projection models are not certainties. RBIs are a volatile stat, highly dependent on runners-on-base opportunities. A hitter can go three or four games without an RBI simply because teammates aren't reaching base, even while hitting the ball hard. Stewart needs the Reds' on-base percentage to hold. His 31 home runs help insulate him (solo shots don't require baserunners), but the margin between a 130-RBI finish and a 115-RBI finish can come down to a handful of bases-loaded at-bats.

For Alvarez, the math works in his favor if the gap is narrow. A Triple Crown contender in September typically sees his highest-leverage plate appearances of the year. Managers stack the lineup to maximize his at-bats. The Astros, likely in a playoff push, have every incentive to optimize around him. If Alvarez trails by five to eight RBIs, closing that gap over 20 games requires only a modest pace advantage of roughly 0.3 to 0.4 additional RBIs per game, well within the range of hot-streak variance.

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Sal Stewart's September Schedule and Reds Context Could Hurt His RBI Opportunities

The strongest case against Stewart winning the RBI title has nothing to do with his swing. It has to do with the batters hitting ahead of him. The Reds are a young team, and if Cincinnati falls out of meaningful postseason contention in September, the lineup around Stewart could thin. Veteran contributors might see reduced playing time in favor of prospect evaluations. Fewer quality at-bats from the top of the order means fewer runners on base when Stewart comes up.

Stewart also faces the universal September risk for rookies: fatigue. He has already logged more plate appearances than any prior professional season. His August numbers were strong, but the 22-year-old has never carried a workload this deep into a season at the major-league level. Even a modest decline in bat speed or pitch recognition over the final three weeks could cost him four or five RBIs, exactly the margin Alvarez might need.

Meanwhile, Alvarez plays for a franchise with deep October experience. Houston's lineup is built to sustain production through September. The Astros' supporting cast generates more baserunner traffic than Cincinnati's, giving Alvarez a structural RBI advantage independent of individual talent.

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What the Market Is Telling You

At 54%, the market is saying Stewart is still the most likely winner of the RBI title, but it is no longer treating him as a comfortable favorite. The 11-point move in three days reflects the market processing a specific piece of information: a credible challenger with Triple Crown momentum, not a generic regression concern.

Whether that repricing is rational depends on the actual RBI gap between Stewart and Alvarez. If Alvarez trails by 10 or more, 54% probably undervalues Stewart. If the gap is five or fewer, 54% may even be generous. The market is effectively pricing an Alvarez surge as a coin-flip-minus scenario, which fits the narrative tailwinds behind a Triple Crown chase.

For anyone tracking this race through the final three weeks, the Pro Baseball RBIs Leader market will move on every multi-RBI game from either player. Stewart's lead is real. The threat to it is also real. The prediction market is the first place where both facts are being priced simultaneously.