The Pirates won last night bumping their record under Don Kelly to 12 and 14 which is a 46 win percentage. Of course the victory was another one run game.
That game was Kelly's 12th one run game as the Pirates manager, and it was a rare come from behind victory for the Pirates. Yesterday's article The Bucs Have Improved Under Don Kelly looked at some surface level offensive numbers under Don Kelly, and it shows the Bucs have regressed in many offensive metrics.
So why have the Bucs improved so much? The biggest factor is the pitching, and boy has it been good.
Since May 9 the Bucs have a 3.41 team ERA which is tied for 6th in the Majors with the Cubs and Blue Jays, and just behind the Brewers. Their 3.8 pitching WAR is 5th in the majors, and 2nd in the NL behind the Giants. The most impressive feat for the Pirates pitching under Kelly is the HR/FB rate. The Pirates lead the majors at 6.7%. The xFIP is right around their ERA meaning fielding has neither helped or hurt the pitching during this time.
The Bucs's rotation has a 2.80 ERA under Kelly, which ranks 3rd in the majors. The bullpen is still struggling with a 4.50 ERA under Kelly and ranks as the 6th worst. For as high as the overall team's pitching is, it is amazing to think there is a lot of room for improvement to be had in the bullpen, and some smaller improvement that may be had on defense. More games with Davis at Catcher, the return of Nick Gonzales, a true first baseman in Horwitz, and continual improvements from Cruz in center should improve the defense as the season progresses.
The Bucs were tied with the 9th highest ERA under Shelton, and the xFIP was significantly lower than ERA under Shelton as well at 3.98 and 4.31, respectively. The Bucs are pitching better and the defense isn't hurting them like it was under Shelton. If you can believe it, the rotation actually had a slightly higher ERA than the bullpen had under shelton, and overall the bullpen was slightly better under Shelton than Kelly.