For one thing, sooner or later it is going to bite him. Relievers can be volatile things and there’s no way to know what days are the days when they’re simply not going to have their best stuff. In a way, making pitching changes is like playing a weighted game of Russian roulette, and the more relievers you use the more chambers you’re loading. I’m not advocating for a Torre-esque strategy of riding the hot middle relief arm until it falls off by any means, but once a guy is in the game there’s no real reason to remove him until you have to if he’s pitching well. That’s true of both Robertson and Joba last night, both of whom threw just 11 pitches in getting 5 total outs (3 of them via strikeout) and allowing no base runners.
But another, more ominous problem is the more straight-forward one; this strategy is putting a lot of stress on the back end of the bullpen. After last night’s game, Mo and Joba have both pitched in 10 of the Yankees’ 15 games, and Soriano has appeared in 8. David Robertson has pitched in 7 games, but for a total of just 6 innings. Which is a shame, because with a 10.50 K/9 and a K:BB ratio over 3.0, Robertson is pitching pretty darn well (and that’s not even counting all of the perfect innings he’s thrown in the bullpen!).
To be charitable, I’m hoping that the early season usage pattern we’ve seen has been a result of the absurd number of off-days the Yankees have had thus far and that things will change starting Friday. Frankly, they almost have to, because there’s just about no way this bullpen could hold up to this workload playing 39 games in 41 days between Friday and June 2nd.