One of the biggest surprises for the first place Pittsburgh Pirates (!) has been the outstanding performance of James McDonald. Before this year, McDonald had a career ERA above 4.00 and a strikeout-to-walk ratio below two, which caused McDonald to alter his arsenal before the season. This year, he has an ERA and FIP under 3.00, with an xFIP and SIERA just under 3.60, thanks to the addition of a slider and subtraction of his changeup.

Before this year, McDonald’s changeup was his third most frequently thrown pitch while his curveball was his main secondary offering behind his two fastball variations. McDonald and the Pirates staff have decided to essentially drop the changeup — down to 3.5% usage after being used over 10% of the time each year according to PITCHf/x. Brooks Baseball has McDonald toying with a slider the past two years, but this year both systems agree that his slider usage has increased dramatically. McDonald now uses the slider as his primary secondary offering, and the addition of this pitch and subtraction of his changeup correlates with greatly improved results on the mound.

The slider has been a tremendous pitch in terms of generating swings and misses, as his whiff rate is above 20% with his slider while his curveball is the only pitch that has a whiff rate above 10%. Here are McDonald’s rates using the slider on two-strike counts, according to Texas Leaguers.

0-2: 18.0% usage, 72.2% strikes, 16.7% whiffs

1-2: 33.3% usage, 65.4% strikes, 25.0% whiffs

2-2: 20.0% usage, 75.0% strikes, 33.3% whiffs

3-2: 11.3% usage, 71.4% strikes, 28.6% whiffs

He increases his usage of the pitch overall with two strikes, aside from 3-2, which is a common fastball count. His whiff rate gets a huge boost with two strikes, especially on 1-2 and 2-2 when combined with the increased usage of the pitch — his 3-2 whiff rate is higher than 1-2 but he uses the slider much less frequently in full counts.

The reliance on his slider as a legitimate out pitch has allowed McDonald to raise his strikeout rate 3% on the season compared to his career, and almost 5% from last season. It is impressive to not only see McDonald add a pitch and succeed with it, but to make the pitch his most frequent secondary offering and it be one of the main reasons for a dominant first half.

As mentioned, along with the addition of the slider, McDonald ditched his changeup. The changeup was an effective pitch in terms of generating swings and misses, as it had a 19.7% whiff rate, which was the highest of any of his pitches last season. The issue with the changeup was the command of the pitch, as it was thrown for a strike just over 56% of the time. In contrast, his slider has been thrown for a strike over 61% of the time this season. It sounds slight, but the improved command of a pitch that is being thrown more frequently along with a higher whiff rate has led to McDonald transitioning from a middle-of-the-rotation arm to a potential top-flight starter.

His ERA is still much lower than his xFIP and SIERA, so expecting McDonald to have this level of performance for the remainder of the year is unwise. He will likely regress, but he is a better pitcher overall now than he was in previous years. The Pirates’ staff deserves a ton of credit for helping McDonald become the pitcher many once thought he could become. Sometimes pitchers like McDonald, who have all the talent in the world but have seen limited success, just need one alteration to send their career in an entirely different direction. The Pirates have found that alteration and are currently reaping the benefits, which may lead to the team’s first playoff berth in 20 years.