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Sunday, March 14, 2010

The Yankees' bullpen candidates, part 3: Alfredo Aceves

For this week's reliever profile, I will turn to the Mexican Gangster, Alfredo Aceves. Signed by the Yankees out of the Mexican League in 2008, Aceves shot through the entire system that year, making his major league debut on August 31st. After making two relief appearances, he replaced the struggling Darrell Rasner as the Yankees' 5th starter in the rotation, where he stayed for the rest of the year. In his six games overall, he compiled a pretty 2.40 ERA despite less impressive peripherals that caused his FIP to stand at 4.80.
The Ace started 2009 at Triple A Scranton, but was called up to the majors before a May 4th game against the Red Sox. He made an admirable long-relief appearance in that game, picking up for starter Phil Hughes. Aceves had many of those types of outings in 2009; in fact, in 29 of his 42 relief appearances, he pitched at least an inning and a third. Since he has been a starter throughout his career, manager Joe Girardi felt comfortable putting him in situations in which he needed length from his relievers. To illustrate Aceves' versatility, I would like to display a double-axis frequency chart: the primary axis on the left shows the number of innings Aceves pitched in each relief outing, and the secondary axis shows the inning that Aceves entered the game. (click on any of the graphs for a larger image)

The graph shows that Aceves most frequently entered the ballgame in the 6th inning, though throughout the season, he entered a game in every inning except the 3rd. Two inning appearances were the most common for Aceves, though he had his fair share of outings both longer and shorter. The other thing about Aceves' appearances is that they were often in relatively high leverage spots. As I discussed a few months ago, the general trend for relievers is that more innings pitched per game, the lower the average Leverage Index will be. Aceves' 2009 season was one of the rare circumstances in which a reliever maintained both a high AIPGR and LI. This next chart shows the LI frequency for each of Aceves' relief appearances (LI of 1 is the "average" situation).

Aceves may be best known for his versatility and command, but his pitches themselves are nothing to scoff at. I turn to PITCHf/x to look at his "stuff."

Average SpeedMax Speedpfx_xpfx_zspin_angle

Nice low-90s fastball, hard cutter, curveball with lots of break, and a changeup with a ~10 mph fastball differential. The fastball is pretty straight - it's presumably a four-seamer, though there may be a few two-seamers mixed in as well. Here are some pitch results to help us judge the effectiveness of the pitches.

Pitch#Pitch%Swing RateWhiff RateWide Zone RateZone Whiff RateChase RateWatch Rate




Looks like some nice stuff there. He can find the strike zone with all four pitches while maintaining a solid whiff rate. One thing I found surprising was the abundance of groundballs from his curveball and (relative) lack of groundballs from his cut fastball.

Aceves has seemed to earn a reputation as a pitcher without patterns, never being predictable with his pitch tendencies. One way I wanted to test this was by splitting up his pitch mix versus righties and versus lefties to see if there was anything particularly unusual. The biggest difference (and understandably so) is in the changeup, which tails into righty hitters. There are significantly more changeups to lefties, so that it can be utilized as moving away from the hitter.

The final chart I would like to display takes into account overall pitch selection based on count. The easiest way to show this in graphical form is to use run expectancy. The ideal pitching situation in terms of run expectancy is an 0-2 count, for which there is a run expectancy of ~ -.1 runs scored below average. Thus, an 0-2 count is displayed as the furthest point on the graph to the left. Conversely, the count with the highest run expectancy is a 3-0 count, which is worth .22 runs above average. The 3-0 count is furthest to the right on the graph. The first pitch of any at-bat always has a run expectancy of 0.
Basically, this graph shows the pitch percentage in each of the 12 counts. I wanted to show some sort of relativity to pitch selection in other counts, so to create this graph I divided the pitch percentage of the given count by the overall pitch percentage. Here is how Aceves used his four pitches, according to the weighted pitch mix (my apologies for the cluttered-ness of the graph).

The general trend, at least for his 2009 outings, appears to be that Aceves prefers the changeup and curveball ahead in the count, and the fastball and cutter for when he's behind.

Aceves began this Spring Training allowing no baserunners in his first 6 spring training innings. He has impressed in 10 innings so far, and even though spring training stats count for virtually nothing, his strong performance has led to whispers about a potential starting role come April. He has impeccable control (his 1.7 BB/9 rate out of the bullpen last year was 4th best in baseball), confidence in all four of his pitches, and enough stuff to fool batters when he needs to. The Yankees have quite an enviable situation, because Aceves would be a welcomed addition to any major league rotation.

Gameday PITCHf/x data is from MLB Advanced Media; it can be easily accessed via this tool. Other statistics are from Fangraphs and Baseball-Reference.

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