Grading the Twins rotation

Scott Diamond shone once more in a day game; for his
short career, his day ERA is 3.32, his night ERA 4.27.

Scott Diamond had his third straight quality start Wednesday, but it was the first time this season he was truly the ground-ball machine of 2012. According to Baseball Reference, he had 13 ground balls and five fly balls Wednesday, bringing him to a 40/35 split for the season.

Diamond's breakout 2012 was all about avoiding walks and getting grounders, so Wednesday was a welcome sign. I'll pick a nit and say I'd like to see him break past six innings next time out; while the bullpen has been very good, the rotation needs to eat more outs.

The Twins have used six starters so far. Vance Worley's had six starts, Kevin Correia and Mike Pelfrey five each, Diamond four, Liam Hendriks and Pedro Hernandez two each.

I classify the starters into three camps:

1) Semi-established: Diamond and Worley. These are the guys I can envision being part of the rotation for the next contending Twins team. Worley's had a difficult go of things so far: 0-4, 7.22 with less than 29 innings in the six starts, and his strikeout rate is down almost two per nine innings.

Indications are that Worley's leash is long, and it ought to be. But he's not doing well.

I'll give Diamond a C for the season so far. Worley has to be earning an F.

2) The disposable veterans: Correia and Pelfrey, the veterans brought in a free agents. I can't argue with Correia's results, even if I doubt he can sustain them. Pelfrey's been brutal. An A for Correia, another F for Pelfrey.

3) The fifth starters: Hendriks and Hernandez. I fully expect the Twins to cycle a number of pitchers through the rotation looking for someone to break through as Diamond did in 2012. Hendriks got the first shot and was quickly supplanted by Hernandez.

I'll give Hendriks a D; he wasn't all that awful in his two starts, but he did get sent down, and unlike last year, he hasn't dominated Triple A upon his return. If and when the Twins swap out another rotation piece, it probably won't be Hendriks getting the call. Cole De Vries and Sam Deduno are more likely (not that either is ready yet).

The left-handed Hernandez has split time between the rotation and long relief since his return, a pattern imposed by the offdays and weather problems, and has put up an ERA of 2.35, which is not to be sneered at. I'll give him a B, but, as with Correia, I don't really expect him to continue at that level.

Here's a key difference between Diamond and Hernandez, at least as far as one can judge Hernandez off 15.1 innings: Hernandez does not appear to be a worm killer. Baseball Reference has him at 20 grounders and 30 fly balls so far.