Tom’s Pitching Lab: The Four-Seam Is Dying and Here is What Pitchers Are Throwing Instead, and Who to Buy.

Sometimes a pitch gets better because a pitcher throws it less

The four-seam fastball is the most popular pitch in baseball. It has been every year since pitch tracking began in 2008. In 2026 it still accounts for nearly a third of every pitch thrown in the major leagues.

It is also following the exact path the sinker walked off a cliff on.

The sinker was once the second-most-thrown pitch in baseball. Over 13 years it lost nearly a third of its usage while the four-seam absorbed the market share and peaked in 2019. The sinker did not disappear. It just stopped being the default answer.

Now the four-seam is the one losing ground — the steepest sustained decline of any pitch in the tracked era. The slider and sweeper group is closing the gap. The chart below tells you where this ends.

Thirty-two qualified starters have already made the switch, cutting four-seam usage by five or more percentage points in 2026 alone. The fantasy reads split entirely based on what they put in its place — and in several cases the ERA is lying loudly enough that you need to act before the market catches up.

MLB Pitch Usage Trends, 2008-2026

IP-weighted league averages. Source: FanGraphs. Slider/SW includes sweepers (classified separately by Statcast from 2023).

The Case Study: How Cam Schlittler's Four-Seam Got Better by Getting Less Attention

The cleanest example of this mechanism in 2026 is not a pitcher who abandoned his four-seam. It is a pitcher who made it better by giving hitters something else to worry about. Cam Schlittler cut his four-seam from 54.7 percent of pitches in 2025 to 44.4 percent in 2026. He tripled his sinker usage from 7.2 to 20.1 percent and grew his cutter from 20.8 to 27.4 percent. What happened to the four-seam as a result? Its run value went from average to the 99th percentile. The pitch got better because hitters could no longer sit on it.

The contact numbers confirm the improvement is real. Barrel rate fell. Hard-hit rate dropped. wOBA against fell 50 points. xwOBA against fell 55 points. His walk rate was cut in half. The ERA (1.87) and xERA (2.76) are both legitimate. Schlittler did not improve the four-seam by throwing it less. He improved it by making it unpredictable.

The Buyer's Board: ERA and xERA Pointed the Same Direction

The evaluation framework for fastball-for-fastball converts is barrel rate and hard-hit rate, not strikeout rate. These pitchers are buying contact suppression. Buy them for ERA, not strikeouts.

Ben Brown is on the IL, which makes him the best buy-on-return candidate in this group. Barrel rate from 11 percent to 4 percent, hard-hit rate from 47.3 to 38.6, a sinker producing .242 xwOBA against with a 63.6 percent groundball rate. The conversion worked. The IL is a timing problem, not a baseball problem.

Yoshinobu Yamamoto quietly dropped his four-seam 7.8 points and his ERA and xERA are both clean. Jesus Luzardo and Shota Imanaga are both running ERAs above their xERAs — positive regression is coming and both are buys. Drew Rasmussen and Dylan Cease have ERA and xERA within a few points of each other. The performance is real.

The ERA Trap Watchlist: Seven Pitchers Whose Numbers Are Lying to You

The more dangerous finding from this dataset is not who to buy. It is who looks buyable and is not. Seven pitchers are carrying ERAs that read as legitimate improvements but xERAs that say the contact quality never actually changed.

Eduardo Rodriguez is the most extreme case: ERA 2.55, xERA 4.64, a gap of more than two runs. Nick Martinez is nearly identical: ERA 2.43, xERA 4.43. Both dropped their four-seam and neither improved contact quality. The ERA is a trap. The xERA is the signal. Sell both before the league catches up.

Davis Martin (CHW) is the name most likely to fly under the radar: ERA 2.41, xERA 3.78 on a fast-rising team that is no longer hiding in plain sight. He belongs on your sell list. Kumar Rocker belongs here too — his cutter is genuinely improving but his xERA of 4.68 against a 3.56 ERA makes him a strikeout play, not an ERA play.

The Two-Step Check. Run It Every Time.

Step one: identify the replacement. Sinker or cutter means a contact play — evaluate on barrel rate and hard-hit rate. Breaking ball means a strikeout play — evaluate on whiff rate and whether the platoon split improved.

Step two: compare ERA to xERA. If both are below 4.00 and moving in the same direction, the conversion worked. If the ERA looks clean but xERA is above 4.25, the ERA is being propped up by luck. Sell into the ERA. The xERA wins that argument every time.

Schlittler and Nick Martinez both have ERAs under 2.50. One is one of the better arms in baseball right now. The other is one of the clearest sells in the dataset. The pitch type is the only thing that tells you which is which before the ERA figures it out on its own. Now you know how to check.

Questions About The Four-Seamer, Answered

Why are pitchers cutting their four-seam fastball usage in 2026?
The four-seam only produces consistent results when a pitcher generates elite vertical ride from spin efficiency. Pitchers without it are moving to sinkers and cutters, which retain velocity while adding horizontal movement that is harder for hitters to read.

Is Ben Brown worth adding in fantasy baseball after his pitch mix change?
Yes. Barrel rate dropped from 11 percent to 4 percent and his sinker is producing .242 xwOBA against. Add him while he is on the IL and hold for his return.

Is Cam Schlittler a fantasy baseball buy in 2026?
Yes. A 1.87 ERA, 2.76 xERA, and a fastball run value in the 99th percentile make him one of the strongest starting pitching targets in fantasy right now.

Why is Eduardo Rodriguez a sell despite dropping his four-seam usage?
His xERA is 4.64 against a 2.55 ERA, a gap of more than two runs that indicates the quality of contact against him did not improve despite the pitch-mix change. The ERA is likely to regress.

How do you evaluate a pitcher who dropped their four-seam fastball usage?
Identify the replacement pitch first. Sinker or cutter indicates a contact-management profile, while a breaking ball points toward strikeout upside. Then compare ERA to xERA. If both are below 4.00 and aligned, the conversion worked. If ERA is low but xERA exceeds 4.25, the underlying performance has not caught up.