A lot can happen over the course of an MLB regular season. That’s why we try to resist prematurely jumping to conclusions with regard to player and team performance. Now that Memorial Day has passed, though, we can start putting more weight behind the numbers we have at our disposal.
After spotlighting the best hitters and starting pitchers from May, we’re doing the same for those guys on the opposite end of the spectrum. Once again, we’re going to rank hitter performances by wRC+, while Skill-Interactive ERA (SIERA) will be used for the starting pitchers.
It’s safe to say that these 10 players are happy the calendar has flipped to June.
May’s Five Worst Starting Pitchers
It seems like pitchers are always evaluated by the same traditional metrics, such as win-loss record, ERA, WHIP, strikeouts per nine innings and walks allowed per nine innings. This is exactly why we’re going against the grain and evaluating pitcher performance by SIERA.
SIERA attempts to measure the underlying skill of a hurler, but unlike FIP and xFIP, it doesn’t ignore balls put in play, and also attempts to give a more accurate picture as to why certain pitchers are better than others. A good SIERA is just like a good ERA — the lower the better.
Here are the five hurlers who struggled the most in May.
The goal moving forward for Lucas Giolito in the Chicago White Sox rotation should be simple: get ahead in the count more often. Overall, the right-hander’s walk rate (14.3%) is higher than his strikeout rate (11.6%). That can partly be attributed to the fact that his 40.8% zone rate and 51.0% first-pitch strike rate are both on track to be career-worst marks.
Injuries to the Arizona Diamondbacks’ rotation has forced Matt Koch into a bigger role with the club than initially anticipated. For someone that doesn’t sport much swing-and-miss capability (12.4% strikeout rate and 5.8% swinging-strike rate), it’s important to control the quality of contact from opposing hitters.
That hasn’t happened so far, as the right-hander has surrendered a 45.9% hard-hit rate and 35.9% fly-ball rate, which has led to 1.69 homers allowed per nine innings.
After a rough 2017 season, Marco Estrada was hoping for a bounce-back campaign with the Toronto Blue Jays. Based off his 5.68 ERA, he’s still searching for it. His walk rate is on pace to decrease for the third consecutive year, but so is his strikeout rate.
Estrada is throwing his four-seam fastball at a 52.3% clip — which is flirting with career-low usage — but it’s still his most used pitch. With that in mind, it’d be helpful if he improved the 192 wRC+ opposing batters have produced against it (117 in 2017).
Reynaldo Lopez has managed to outperform his season-long SIERA thus far (5.21 SIERA, 3.80 ERA). However, the peripherals tell us he’s not all that different from Giolito. The right-hander has become much more reliant on his slider, too. After throwing it 2.2% of the time in 2017, that number is currently sitting at 19.9% this year.
To accommodate this spike in usage, Lopez’s curveball (12.9% to 5.2%) and changeup (23.7% to 16.5%) have both taken a step back. That slider has easily been his best pitch to-date, evidenced by a 42 wRC+, 30.0% strikeout rate, and 14.8% swinging-strike rate.
Danny Duffy didn’t like hearing his name pop up in trade rumors over the winter. He may not have to worry about it much this summer if he doesn’t get himself back on track soon.
The southpaw has never been much of a ground-ball pitcher, but his current 33.0% rate would be his lowest since 2013 if the season ended today. It doesn’t help that his soft-hit rate (12.7%) and hard-hit rate (39.5%) would also both be career-worst marks.