The Chicago White Sox have a new starting pitcher in the mix for their opening day roster, having signed veteran right hander Dominic Leone on February 14th. The 32-year-old bounced around in 2023, after two straight solid seasons in the Bay Area with the San Francisco Giants. In 2023 Leone combined to pitch to a 4.67 ERA over 54 innings between the Mets, Angels and Mariners.  

Leone ended the year in Seattle with a 4.35 ERA over 10.1 innings of work after the Mariners claimed him off waivers. However, he had a dreadful time with his control as he walked 8 batters in those 10.1 innings.  Not only did he walk a lot, but he also allowed 5 home runs as well. 

Although it was a small sample size with the Mariners, in his full season he didn’t fare better. He pitched to a 5.30 xERA (expected ERA) over those 54 innings, allowing 4.7 walks per nine and 2.3 home runs per nine.  

Still, the White Sox still saw enough to give him a minor league deal with a spring invite as he’ll look to make his ninth MLB club in his 11th big-league season.. And while his 2023 was horrendous, there is some logic to that. 

In the previous two seasons with the Giants, Leone was very solid. After a very good season in 2021, where he pitched to a 1.51 ERA over 53.2 innings. He followed that up with a solid 4.01 ERA over 49.1 innings in 2022. Combined that’s a 2.71 ERA over 103 innings. And while his walk rate was still pretty high, he limited home runs way better than in 2023 at 0.7 combined per nine over those two years combined. 

In those two years his xERA was solid in both years with 3.37 and 3.72 in back-to-back years. By far it was his best stretch as a big leaguer. Main difference in those two seasons was effectiveness of his slider: 

Looking at those numbers you clearly see his slider not having the results from 2021. It has been a steep decline from a positive 8 Run value in 2021, to positive 3 in 2022 and 0 in 2023. While his fastball always had his issues, his main out pitch declined. So why did it decline? 

Looking at the numbers, Leone didn’t do a lot different with the pitch himself. His spin rates were about the same, and his inches of drop kept being amongst the league best. The main difference I spotted was his mph. In 2021, he actually threw his slider slightly slower than the other two seasons mentioned (83.7 to 85.1). To me such a small difference wouldn’t account for that decline. 

So, is location the issue? I don’t think so, as the location of his slider, hasn’t changed that much. To me these screams hitters adjusting to his slider. If you look at the launch angle, the hitters are able to put the ball in the air more. And with him increasing the home run total he allowed, it could be a sign. Which is impressive from hitters as his location is still down in the zone the most times, he throws his slider.  

So, look for his slider this spring. If he gets good results with that pitch, it’s a major difference. The first step for Leone to make a new impression with his new team. He likely won’t make the final roster, but you never know when they need a reliever. A good spring will put that in the memory of manager Pedro Grifol and his staff. And we know he has the experience to handle himself.