At this point last year, Thomas Harrington was one of the Pittsburgh Pirates’ best prospects, and a consensus top 100 prospect across the entire sport. He had a legitimate chance of grabbing a rotation spot early in the year, but he missed out on the opportunity after struggling to start the season. He pitched 96 innings at Triple-A, where he had a 5.34 ERA, a 21.7% strikeout rate, 8% walk rate, and 1.88 HR/9 ratio. He also played a few games at the Major League level, and allowed 15 earned runs in 8.2 innings.
When Harrington pitched at the Major League level, he threw four different offerings. His four-seam fastball was his most used pitch. That was followed by his splitter, sweeper, and cutter. However, there are a few pitches he never utilized at the Major League level that he used semi-frequently at Triple-A. One of those pitches in particular could be the key to breaking out as a quality MLB starter in 2026.
That pitch is Harrington’s curveball. Harrington dominated Triple-A opponents with this pitch. He induced an impressive 44.4% whiff rate. That was the 28th highest whiff percentage on a curveball by any minor league pitcher who threw at least 100 curves. Opposing hitters didn’t have one single barrel against him, that is when they made contact against the pitch. That also means he didn’t give up a single home run with his curveball. The right-hander held opponents to just a .180 xwOBA when using this offering. This was the 26th best mark by any pitcher who threw a curveball 100+ times.
Harrington utilized his curve 7.4% of the time. He threw it 120 times in total, though that is 120 times more than he did in MLB. It averaged out at 79.4 MPH, which is similar to the MLB average of 79 MPH from 2025. He threw the pitch with both vertical and horizontal movement. Harrington’s curveball dropped 54.6 inches and had 13.5 inches of glove-side movement. Both were better than the average at the MLB level in 2025. Among the pitches Harrington threw 100+ times at Triple-A, his curveball induced the highest whiff rate, lowest xwOBA, and the best barrel percentage.
There’s no question Harrington has the control to make a good pitch work as well. He receives positive reviews about his ability to locate, both by BA and MLB Pipeline. In 2024, he only walked 4.1% of opponents. That was the fourth lowest BB% of any minor league pitcher with at least 20 games started. His 21% K-BB% was also the 24th highest among the same set of pitchers with 20+ games started.
The fact he didn’t use his most effective pitch once at the Major League level is strange. Even though it wasn’t his primary offering, he still used it semi-frequently, and induced outstanding results. This isn’t just an above-average pitch, but one that gives batters a different look from his other offerings. If Harrington starts incorporating this as a main part of his arsenal in the Major Leagues, he may finally take a massive leap forward in 2026.
