On June 2nd, Robert Stephenson was traded to the Rays in exchange for Alika Williams. As of this writing, with the Rays, Stephenson has posted dominant numbers and has been a steady performer in an uncharacteristically inconsistent Rays bullpen this year.
Team | IP | K/BB | ERA+ | FIP |
w/ Pirates | 14 | 17/8 | 89 | 5.33 |
w/ Rays | 35.1 | 55/8 | 184 | 2.30 |
There was seemingly one large adjustment Stephenson made upon his arrival in Tampa and that was to completely ditch his slider and replace it with a cutter. Here’s his pitch usage for the 2023 season broken down by month.
It’s easy to see the drastic plummet of the slider usage right at the beginning of June. Now I think it’s important to look at the differences between Stephenson’s slider and cutter to understand why (and if) this adjustment is what has led to his increased effectiveness.
I went and looked back at all the sliders Stephenson threw during his time with Pittsburgh this year (Opening Day – 6/2) and also all the cutters he’s thrown with Tampa (6/3 – present). The biggest observational difference between the two outside of the shape is that the cutter’s action occurs later and is quicker than the movement his slider produces. Despite Stephenson’s slider averaging almost 3,000 RPM’s, the break of the offering starts pretty early out of his hand, especially compared to his cutter which breaks noticeably late. Here are a couple of examples- early season slider in the first video and a recent cutter in the second video:
I don’t come to the conclusion that Stephenson’s slider is a bad, or even a below average offering. I see it as his cutter being such a good offering that it eliminates his need to utilize the slider at all. His ability to command the cutter and the previously mentioned exceptionally late movement allow him now to essentially pitch off of it.
The other notable pitch-mix change with Stephenson after the trade was his increased usage of his splitter. The month of September Stephenson has used his splitter 14.7% of the time, the highest of any month for him outside of June where he threw it 17.6% of the time. Stephenson almost exclusively uses his split-finger against left-handed hitters and the offering has done wonders at neutralizing those hitters this year. Stephenson has thrown 80 splitters this year (77 vs LHH’s) and batters are slugging .166 off the pitch and posting a .106 wOBA. Let’s take a look at a couple of these splitters from Stephenson:
Stephenson’s split-finger averages 88.8 mph and as of this writing has posted a 40.9% swing/miss rate with the pitch. As you could see from the two previous videos, what makes it such an effective offering to me is his command and ability to manipulate depth on the pitch. When Stephenson is trying to land it in the zone, the offering has late, slight depth to it like the one in the above video against Bryce Harper. However, when he’s looking to expand with it to get a swing and miss he often gets significantly more depth on it and is effective because that depth still happens late enough that it’s able to generate a 31% chase rate.
As the playoffs approach, Stephenson will be pitching some of the highest leverage innings of the year out of the Rays bullpen. Some of my favorite stories each year revolve around pitchers tweaking their pitch-mix or adopting a new grip on an offering that takes them to a new level and Stephenson has been the poster child for that this season.