I don't believe Tommy really has a slider. His slider is his cutter. At times, he took enough off of it and/or had enough movement on it in previous years (i.e last year) that it fooled pitch fx into thinking it was a slider, and it was basically a defacto slider. But, you bring up a good point (and I agree) that he's not using that pitch this year like he did last year, and he clearly isn't having the same success against RHB's that he enjoyed last year.
There appears to be a pretty clear strategy to have him focus more on the curveball as his breaking pitch. For example, this year he has 27% curveballs against RHB's as compared to only 15% last year. Its a tough balance, because on the one hand, his curveball has been much sharper with more depth and consistency this year. On the other hand, there's not the same deception he had mixing in the cuttter (i.e defacto slider) and fastball that he had last year
The issues with LHB's is quite a bit different imo. There clearly seems to be a strategy to pitch more to the outside corner and reduce the "damage" from last year. Also, less cutters in. I think Norris is doing basically the same thing, sequencing a lot of 4 seamers and 2 seamers off the outside corner. Seems to be limiting the HR's for Tommy but a lot of hard hit balls the other way.
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