Just keep on walking, Zach.
I should preface this by saying I've never been a Zach Stewart fan. After he came over to the White Sox and pitched in a few big league games my reaction was "This is a guy who was a well-regarded prospect?" His fastball looked like something Kenwo could hit and the rest of his stuff was sub-par.
But I didn't have a problem trotting him out there in 2011. It was a lost season so let him get his innings. Maybe he gets back whatever scouts saw in him (if he indeed ever had it) or otherwise figures out a way to get hitters out.
I have a problem with it now. I'm always the first guy to tell people not to get worked up over the last guy in the bullpen. He wouldn't be the last guy if he was good. But he should be able to give you replacement level performance. And Stewart has been incapable of that.
There are also other options. But I'll get to that later. First, let's take a look at Stewart's résumé.Batters are hitting .332/.370/.531 against him in his MLB career. Basically, he makes every hitter look like Matt Holliday. And it's pretty easy to see why. Back when he was a prospect, he allegedly threw 92-95 MPH. When he came to the White Sox last season, it was more 90-92 MPH. And now it's more 88-90 MPH. Out of the bullpen. He apparently missed the memo that one should throw harder as a reliever.
His slider, which was allegedly a swing-and-miss offering that was better than his fastball, just looks like a cookie a lot of the time. And he's throwing his changeup more often this season but it's not particularly clear why. He basically doesn't have anything that looks like a major league pitch.
Jose Quintana will be getting at least one more start before John Danks re-claims his spot in the rotation. Given his performance, there are already calls for Quintana to stay with the White Sox in the bullpen (or the rotation - let's not go overboard, folks). Sure, there would be quite a few lefties in the pen but handedness really shouldn't be much of a consideration for a long reliever, whether that would end up being Quintana or Hector "How much further can I fall on the depth chart?" Santiago.
The more persuasive argument against Quintana staying is that the White Sox will want to keep him starting games regularly so if/when a starter is needed, he'll be fully prepared. There's also the matter of his development as a pitcher, which is far from complete. The needs of the major league club usually trumps development but, when we're talking middle/long relief, that falls away.
Another option is to call on the guy who lost out to Stewart for that last bullpen spot: Dylan Axelrod. Axelrod at least has shown some ability to get major league hitters out. While he struggled in his only start this season, he showed some acumen in his two relief appearances, including getting Nate Jones out of a bases loaded jam in Boston. And he's been pitching just fine at Charlotte.
The last guy in the bullpen, just like the last guy on your bench, should usually be readily disposable. This doesn't mean a team should be showing up on the transaction page every other day like the Athletics or Rays seem to do. Activity for activity's sake is silly and probably bad for team morale. But, after you've given those guys a decent opportunity, you should re-evaluate.
Zach Stewart has had two months to show why he's worth keeping. He hasn't shown it. Whatever roster machinations are to come in the next week or two, one of the outcomes should be Stewart in Triple-A.