I really hope Hammel's woes are because of being rusty from Buck's ST strategy, rather than him not trusting the knee. I highlighted in his thread that his 2-seamer has not been there this year, and that's killing him, IMO.
Hammel's .79 GB/FB ratio this season is much more in line with what it was in Colorado, than his 1.14 ratio here in Baltimore last season.
He's thrown his 2-seamer 29.1% so far this season at an average velocity of 92.4 MPH so far this season. Last season to this point, he had thrown his 2-seamer 42.9% of the time at an average velocity of 93.3 MPH.
So he's thrown the 2-seamer about 14% less, and at almost a MPH slower. The spin rate has also decreased quite a bit on that pitch, according to Pitch F/X data.
It's a small sample size, but his bread and butter has not been that effective quite yet. We all know his limited work in the spring, as well as the knee issues last year, so it shouldn't come as that much of a surprise, but hopefully he's just building up to getting back to where he was, because his 2-seamer needs to come back into the fold and be as good as it was last year.