By The Numbers: Clayton Mortensen

With the second-most wins and the 10th best ERA in the league, Clayton Mortensen has been one of the best starters in the Pacific Coast League this season. But what will it take for Mortensen to find success in the major leagues? Nathaniel Stoltz takes a look at Mortensen's major league pitch data and comes to some conclusions...

The early returns on righthander Clayton Mortensen, acquired about a year ago in the Matt Holliday trade, were mixed at best. He posted a mediocre 4.45 ERA in Sacramento and was lit up for a 7.63 ERA in the majors last year. Mortensen also entered 2010 at age 25, and at that age, he certainly needed to show something to remain more than a fallback Triple-A type in Oakland's long-term plans.

The core of Mortensen's issues in his first major league stint was a complete inability to strike hitters out—he only got 13 Ks in 30.2 innings, which isn't going to get it done. Mortensen did show okay control, walking just 13, and he got a 52.1% groundball rate, but you'd have to have Cliff Lee's control and Brad Ziegler's groundball ability to get away with striking out under four batters per nine innings.

Looking at Mortensen's pitch patterns, it's easy to spot a big problem—he only threw first-pitch strikes to 52.4% of the batters he faced in the majors in 2009, 20th worst in the majors among starters with at least 30 innings. If you don't have plus stuff—and while Mortensen's three-pitch arsenal isn't poor, it hardly stands out in the majors—you have to get strike one far more consistently than that.

Paradoxically, Mortensen actually got a strike 61.8% of the time overall, so it wasn't like he couldn't get the ball over the plate. Instead, what seemed to happen is that he fell behind and then had to throw the ball over the plate behind in the count. That ended quite predictably with the 7.63 ERA.

The one piece of good news that came out of Mortensen's 2009 major league stint is that his breaking ball, a hard slider that went for a strike 66% of the time and induced a swing-and-miss 14% of the time it was thrown and 30% of the time it was offered at, proved to be better than advertized. It looks like a well-above-average MLB pitch rather than the average offering most scouts thought it to be.

Conversely, it was Mortensen's bread-and-butter sinker that got him into trouble. He threw it for strikes far less than either of his offspeed pitches, which explains why he fell behind in the count so much, because like most pitchers, he goes with the fastball early in counts. In addition, it only induced a swing-and-miss 2% of the time—a paltry 1 in 50 sinkers was whiffed at.

His troubles with the sinker are thus self-perpetuating—he'd fall behind in the count almost half the time, and then have to throw a sinker in the zone, rather than getting ahead and getting to work with the slider more. The lack of two-strike opportunities for the breaking ball go a long way in explaining Mortensen's low strikeout rate.

Therefore, in order to improve his MLB performance beyond 2009's poor levels, Mortensen has to have better command of the sinker and do a better job of attacking hitters with it early in counts so he can get to his better pitches. Throwing the slider earlier in counts might also be a good idea, and in his one big league start in 2010, Mortensen started off half the batters he faced with offspeed pitches. Not coincidentally, he threw six strong innings, striking out seven batters—over half as many as he did in five times the innings last season.

Mortensen has, of course, spent most of 2010 in Triple-A. Last season, with Sacramento, he struck out just 12.4% of batters he faced, but he's seen a nice jump to 17.5% this season. Simultaneously, he's cut his walk rate from 9% of batters to 7.3%, a sign that he's either using the slider more or getting better with attacking with the sinker early in the count.

The evidence points toward the latter of those two possibilities, which is nice for two reasons: a) throwing sliders more than a third of the time isn't a good idea for a starter, because that increases the likelihood of injury, and b) going away from the sinker could compromise Mortensen's nice groundball rate.

But actually, Mortensen has seen his grounder rate jump from 49.6% in Sacramento last year to 52.3% this year, so the change in the rest of his stats is most likely due to getting more aggressive with the sinker. For what it's worth, his pitch distribution in his one major league start this year wasn't much different from what he did last year—he threw a few more sliders and slightly fewer changeups than he usually did in 2009, but nothing out of the ordinary.

Mortensen's sinker isn't likely to ever be any sort of swing-and-miss pitch, and his changeup isn't particularly good either, so it's doubtful that he'll ever have the stuff to be a high-strikeout pitcher who sits in the front half of a rotation. More likely, he could be a useful back-of-the-rotation starter, although Oakland, with good young rotation depth, may not be the right organization for him to have that role in.

For the A's, he may be best used out of the bullpen, where he could unleash the slider and become a poor man's version of current Oakland reliever Michael Wuertz. Mortensen could also be useful to a team like the Pirates in a starting role, but unless the A's get a good offer for him, they're best off letting him get back to the majors and have some more success to build his trade value up some.

To read more from Nathaniel, visit his blog at The Bleacher Report and

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