Pitcher Potpourri: Trevor Williams, Joe Ross and Caleb Thielbar find homes

All those guys signed in the final days of 2024, inking modest deals for National League clubs. Here’s something about all three.

Trevor Williams re-signs with the Washington Nationals

Williams is a strange case. In 2023, his fastball was destroyed. That wasn’t a big surprise: The pitch averaged 89.7 mph with only 11 inches of induced vertical break. Williams gave up 34 home runs that year; most of the damage was inflicted on his four-seamer.

In 2024, he actually lost a mark from his fastball, dropping to 88.9 mph; the motion profile was almost identical. Yet during his injury-shortened 66.2 innings of work, he dominated hitters with the “heater.” Williams allowed just three home runs last year; only one broke away from the four-seamer. The value of runs in the field went from -0.8 runs per 100 pitches in 2023 to +3.2 in 2024. What has changed?

Positions, for example. While watching a random Williams start against the Orioles in May, I heard the Nationals color commentator note that the right-hander was successfully keeping hitters off-balance with a mix of high and low fastballs, marking a change from his approach in 2023. Position charts, courtesy of Baseball Savant’s Pitch Highlighter tool, bear that out.

Here are all of Williams’ 2023 four-seam fastballs located in the “shadow” zone. Note the density of the pitches on the upper track and the scarcity at the knees:

And here’s the same pattern of deep-zone fastballs in 2024. If anything, Williams has been targeting the back of the zone more frequently, leaning into the pitch’s natural sinking qualities:

As I often write on this site, proposals do not exist in a vacuum. When a batter steps up to the plate, he must account for all the offerings in the pitcher’s back pocket. Increasing the usage of one pitch could therefore influence how hitters respond to another (seemingly unrelated) pitch. In Williams’ case, the most used court was his libero.

Williams is an extreme supinator; his fastballs have an average spin efficiency of just 67% with a 17-degree arm angle. This motor preference lends itself to throwing breaking balls with plenty of horizontal motion, and it’s what Williams has added to his game in 2024. His sweeper usage increased from 3% in 2023 to 21% in 2024, making it his second most used pitch after the four-seamer.

Sweeper amplification expanded the speed range and horizontal movement band in Williams’ overall arsenal. Hitters whiffed 47% of the time they swung at the pitch, which is a ton. But the sweeper likely had secondary effects on the fastball. Batters could no longer sit on a couple of pitches in a narrow window of movement and velocity; now they had to think about the big flex sweeper, and as a result the fastball probably worked better.

Frankly, none of these changes would matter much if Williams wasn’t such a gifted command artist. As I mentioned in his blurb on the 50 Free Agents, he is considered the best in baseball based on Driveline’s missed yardage metric, hitting targets better than any starting pitcher. No one launched their sweeper less frequently into the heart of the area; by throwing his pitches where hitters can’t hurt him, Williams maximizes his low profile. He’s never been a workhorse, but at two years and $14 million, the Nationals are paying the sixth-highest starting price for someone with an 80-rank command. Even with the obvious limitations, he seems like a solid bet.

Joe Ross signs with the Philadelphia Phillies

Ross is an old-school low-slot sinker/slider guy, throwing those two pitches about 75% of the time in 2024. Against right-handers, the game plan is simple: put sinkers on hands, throw sliders away.

But Ross is unlikely to face exclusively right-handed hitters. The Phillies initially signed him in contract negotiations with the idea that he would be their fifth starter. After the Jesús Luzardo trade, it appears he will play more of a swingman role if all five starters remain healthy. But even with reduced responsibilities, Ross is expected to retire a bunch of lefties in multi-inning appearances.

In theory, lefties are a problem for Ross. For his career, he has allowed a .353 wOBA to these opposite-handed opponents. (Right-handers, meanwhile, have wOBA just .283.) But last year, Ross had no visible platoon split, and he achieved that platoon neutrality by using lead as the primary pitch to lefties.

Generally, this would be seen as a problem. In 2024, left-handed hitters as a whole hit .284 with a .441 slugging percentage against right-handed sinkers. Against Ross they did much worse: they hit .171 off the field and hit just .317.

How did Ross limit his opposite hand damage against his sinker? It wasn’t due to motion: With about nine inches of induced vertical break and 13 inches of arm-side travel, the pitch is basically a generic two-seam fastball. But speed is an advantage: the throw averaged 95 mph, and Ross can get up to 98. And when Ross hits his primary target, the throw is virtually uncatchable. Or at least non-swingable.

Against lefties, Ross usually targets the front hip, looking for pinpoint shots. And when it works, it really works. Admire this backward K from Corbin Carroll: When done correctly, it’s one of the greatest pitches in baseball:

But the anterior hip lead is a dangerous game to play. The side of the arm is just a little missing and that means running straight into the ideal left-handed swing path. Speed ​​gives Ross some margin for error, and last season he mostly got away with errors, allowing just two extra base hits out of the field. But mistakes like this may not happen so innocently in gloves this season:

Ross also occasionally targets the outside half, although he hasn’t hit that target as successfully. And these outside-half sinkers caused him the most problems: Pavin Smith and Jarred Kelenic both launched targeted shots deep into the opposite stands.

Given the current state of the Phillies’ pitching depth and the size of the contract (one year, $4 million), the stakes aren’t necessarily that high. But if one of the team’s starters falls, Ross will play a vital role at a club with serious championship aspirations. I fear that in a large sample the platoon’s problems could come back to haunt him.

Caleb Thielbar signs with the Chicago Cubs

Moving up the arm angle ladder, we now come to Caleb Thielbar, the left-handed reliever who signed a one-year, $2.75 million contract with the Cubs on New Year’s Eve.

After a series of effective seasons in Minnesota, the wheels came off in 2024; Thielbar’s walk rate increased, as did his ERA. Control issues have always been part of the risk profile of a pitcher like Thielbar, who throws two distinct balls with enormous movement. There’s the 12-6 curveball, a somewhat expected break profile from a guy with Thielbar’s exaggerated arm angle:

And then there is the street cleaner, decidedly unexpected:

Landing both pitches in the strike zone is a tightrope walk, especially with those jerky mechanics. In 2024, Thielbar fell off the edge, walking 11% of batters he saw. Double-digit walk rates and a 92 mph fastball aren’t going to cut it in a major league bullpen, but last year was the first season Thielbar really struggled with command, and the strikeouts have always been there. At the price they signed him, the Cubs are counting on him to fill the left-handed specialist role with ease. It’s a modest ambition, but it’s an ambition nonetheless.