Lucas Giolito returned to the mound for the Boston Red Sox last week, after over a year on the injured list. He’s been recovering from a UCL tear sustained during spring training. This spring, he was delayed by a hamstring injury. He is finally healthy enough to pitch again, and the results have been rather mixed.
Giolito made his first start against the Toronto Blue Jays in Toronto. He started strong, and while the last inning skewed his overall numbers a bit, he still had a quality start. His second time out against the Texas Rangers, however, was a different story. He got shelled and was ultimately pulled in the fourth inning.
At first glance, it would appear that the two starts were very different, and there is not much to glean from Giolito’s performances other than rust. There is one element that is a bit worrisome, though, that was a factor in both outings despite different results: pitch repertoire. He threw just two pitches in his second start, which was very similar to his first.
Lucas Giolito has had a successful career overall. In 182 regular-season appearances, including 180 starts, he has compiled a 61-63 record and a 4.47 ERA. His best stretch came when he was pitching for the Chicago White Sox from 2019-2021. The pitcher has been a workhorse in his career, consistently soaking up innings even if he has had some struggles with performance.
That is, until 2024, when Giolito had his first major injury. Since that time, he had not thrown a pitch in the majors until May of this year. He was not able to eat innings for the Red Sox, and even in his most recent start, his struggles ended up taxing the bullpen. One or two short starts here and there happen, and thus he cannot be judged purely on that game. The Red Sox need him to take innings away from the bullpen, though, which is thin and struggling in high-leverage situations.
For Giolito to have the success the Red Sox need out of him, he needs to perform at the level he has in the past. Surviving in the league as a starter requires a decent pitch arsenal that can keep hitters off balance multiple times through the order. Since 2019, when he dropped a sinker out of his repertoire, Giolito has relied on a total of four pitches: fastball, slider, curveball, and changeup.
Gioloto’s primary pitches have always been fastball and changeup, although he typically throws almost as many sliders as well. The curveball is a relative rarity throughout the season. Still, three pitches thrown at pretty consistent rates are enough to get through orders. So far this season, though, he has nearly completely cut out the slider as well. Out of 164 pitches thrown this year, only nine have been a slider or curveball, and most came in that first start in Toronto.
By using this approach, Giolito has placed a huge focus on fastball command, given that he has thrown it nearly 60% of the time. The problem with this is that when the fastball command is not there, he cannot be successful. In Tuesday’s start against the Texas Rangers, that was the exact problem. He is getting hit hard high in the zone. His velocity and spin rates on all his pitches have been at his career norms, and even his whiff rate is essentially the same. He is just missing some of his spots.
Missing spots is not always a death nail for pitchers, except when they refuse to throw other pitches. Players know a fastball or changeup is coming. They can sit on the pitch they want, get good looks, and then hit it. That simply is not enough of an arsenal to keep players honest, especially when they are not being located that well.
Giolito needs to find his comfort with his slider to turn this around. Two games are not any reason to panic, they are very small sample sizes in terms of data. Losing the feel of a pitch that was previously thrown anywhere between 15-30% of the time on any given season, however, will cause dramatic changes in profile. The team needs to determine why this has happened and what can be done to address it.
Lucas Giloito is essential to the Red Sox success this season. Their rotation can match up in the American League, but only if he is pitching at the level he is capable of. Garrett Crochet is a legitimate ace, Brayan Bello and Tanner Houck have solid mid-rotation ability, and Walker Buehler has a high ceiling as he continues to find consistency coming off injuries of his own. Giolito is a fantastic final piece to that rotation, one that could do well in the postseason.
That is not going to happen, though, if Giolito is only throwing fastballs and changeups. He needs something more, and that something is likely the slider. The team needs to pounce on that and figure out why he has ditched it and how to get it back. Hopefully, as that develops, we will see the pitcher we saw when he was with the White Sox, because that is something the Red Sox desperately need right now, as they battle to stay above the .500 mark.
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