Posted by Michael Street on Tuesday, September 8, 2009 at 11:27 pm

After starting out so well, Junichi Tazawa struggled in his last two appearances, both against the White Sox—but his opponent isn’t the only thing those two outings had in common.

In both outings, he got behind hitters and had to pitch down the middle of the plate, but the reason he got behind was a lack of control of his breaking ball. His repertoire has been a four-seam fastball with some late movement, a curve, and a splitter that serves as his changeup.

If you look at the Pitch-F/X from his first start below, you’ll notice two things. (And thanks to Zach Sanders for putting together these awesome Pitch F/X charts for me!)

First, his pitches are largely on the inside half of the plate to a RHB) In general, you’d like to see him work the entire plate, but staying on one side or the other is better than pitching over the middle of the plate. Work one side of the plate too often, however, and batters pick up on it, the way A-Rod did by jacking an inside curve over the fence to win the game.

The second thing you notice is that Tazawa’s curve is particularly nice, slicing the inside half of the plate and the bottom half of the zone. Generally, RHP throws curves to break away from a RHP batter on the middle or outside of the plate. Using it as a backdoor curve is still fairly effective, if it isn’t overused, which (again) can lead to batters sitting on it the way A-Rod did.

Tazawa hasn’t used his other breaking pitch, identified here as a slider, since that first outing. You can read my last column about Tazawa to read some of the discussion about what, exactly, the pitch is—I’m calling it a shuuto, the reverse-slider Japanese pitchers often use, but it’s hard to know for sure until we see it more.

Now, let’s look at his August 27 start, when he gave up 9 ER in 4.0 IP.

That curve comes in right over the middle of the plate from both the side and top angles, a real problem. His other pitches are fairly well-placed, with his splitter/change grazing the bottom half of the zone. He also achieves decent separation among the pitches, using most of the plate.

But that separation’s only effective if he’s pitching ahead of batters, which didn’t happen in this game. Over and over in the early innings, Tazawa couldn’t hit the strike zone with his curve, fell behind batters and had to throw his four-seamer over for strikes.

And because his fastball barely touches 90, he’s not going to get away with too many of those pitches when batters are waiting for the heater. On top of this, he lost 1 MPH from his 8/22 to his 8/27 start, making his fastball that much more hittable.

Eventually, Tazawa got his curve under control in some of the later innings—that’s why the curve appears to be in the middle of the plate, since this is an average plot of all his ABs—but by then it was too late, and he was already well behind.

You can also see from where the curve is breaking that it’s breaking much sooner than it did in his first outing. That could allow batters to pick up on it sooner, and given where he’s throwing it, it turns from a backdoor curve to one sitting over the heart of the plate.

That inside curve also does a poor job of setting up batters and using the entire plate. If you compare this plot to his 8/22 start (the 6.0 IP blanking of the Yanks), you can see the difference:

Here, his curve is nicking the bottom and outside of the strike zone, and you can see he’s using the whole plate and setting up hitters. When he does that, he can get away with throwing the four-seamer over the middle of the plate. Batters watching the outside and inside corners will be fooled.

Spreading those pitches across the plate will keep changing batters’ eye levels and keep them off balance. With that splitter/change clipping the bottom of the zone, he’s also going to get some tough calls on unhittable pitching.

As his starts have progressed, Tazawa has clearly had problems with his curve, which has flattened out. The stats bear this out, too. Looking at the average horizontal and vertical break of his curve in his five starts, here’s how they correlate:

That’s a strong decline in both axes, indicating the curve is staying up in the zone, and possibly that he’s just losing his feel for it, which can happen with a curveball. He loses some side-to-side break, but it’s flattened out, with a break that’s almost halved by his latest appearance.

And the trend is disturbing, most particularly in that last start, the second time he was shelled by the Chicago White Sox, on Sept. 4.

Some of that is no doubt due to the fact that Tazawa entered as a reliever. Paul Byrd had already given up seven runs in 2.1 IP, and  Terry Francona needed to get him out of there. He’d wanted to save Tazawa for the next night, in case Tim Wakefield ran into trouble, and he likely told Tazawa as much.

Instead of getting the night off, Tazawa had to enter as a reliever when he likely wasn’t prepared, didn’t have much time to warm up, and came in with one out and one on. Small wonder that he struggled, then.

The F/X on that outing also shows his struggles:

The fastball and curve are hitting almost the same spot in the strike zone: dead center. If a pitcher doesn’t vary location with the two pitches, particularly if that curve is flattening out, he’s going to get hammered—and that’s what happened to Tazawa.

His splitter is also falling entirely out of the strike zone, meaning batters won’t swing at it and umps won’t call it. The combination of all these factors led to a 3.2 IP outing when he surrendered 5 runs, his second bad outing in a row

One thing we haven’t seen enough of is Tazawa’s slider/shuuto, which might complement his repertoire better when his curveball is failing him, as it did both of the last two starts. Particularly with the reverse break a shuuto has, it could change up RHB who will start to look on the outside of the plate for his curve.

For now, Tazawa will continue to work out of the bullpen, which means he’s not only going to have to regain command of his curve, he’s going to have to get ready quickly, the way he didn’t do on the September 4 outing.

The increased rest he’ll get as a bullpen pitcher may allow him to regain some strength and perhaps get his feel for the curveball back. He may also get to work on that shuuto/slider we saw early on, an excellent fourth pitch that would give him one more breaking ball to work with.

At this point in the season, Tazawa will be the Boston longman out of the pen, an important spot down the stretch, as Byrd and Wakefield are both question marks, and he may be called on for more inning-eating duty. Going into the playoffs—assuming Boston makes it—he needs to prove his worth so that he’ll stick on the postseason roster.

He’s still showing plenty of promise, and a young pitcher is going to struggle, particularly one in just his first pro season. Because he lacks dominating stuff and a strikeout pitch, command of the strike zone and control of his breaking pitches will be key to his success going forward.

Thanks again to Zach Sanders for some beautiful Pitch F/X graphs!