Lots of Groundballs from Affeldt

Over this past off-season Brain Saeben surprisingly made a number of free agent acquisitions that were well received in the sabermetric community, including signing Jeremy Affeldt to two year eight million dollar contract. Affeldt has already provided 3.2 million dollars of value, so is well on his way to earning his contract. A big part of his value comes from the fact that he has allowed only one home run so far this year on the strength of his amazing 66% GB/BIP, as of last night good for third below only side-armers Brad Ziegler and Peter Moylan. That is way above his career average of 48%, although his GB rate has been increasing each year since 2006.

Usually such a high GB rate is achieved by throwing a ‘sinking’ fastball. Most fastballs ‘rise’ about 8 inches, that is they drop 8 inches less than you would expect due to gravity. A sinking fastball ‘rises’ a lot less than a normal fastball, so appears to sink to hitters. A sinker will generally have a vertical movement between 4 and -4 inches, so drops between 4 inches less to 4 inches more than you expect due to gravity. Here is the average vertical movement of the fastballs of the eight relievers with a GB rate above 60%. They are ordered along the right.


Affeldt’s fastball rises the most of the group, almost as much as an average fastball. Most of the group has heavy sinking action to their fastballs, as expected. In addition most of the group throws two-seam fastballs that tend to sink more, while Affeldt throws mostly a four-seamer that tends to rise. Affeldt’s high GB rate is very strange given this graph.

The next thing I thought was that even though Affeldt’s fastball rises he can locate it down in the zone. So I looked at the location of his pitches in 2008 and 2009.


The 2009 pitches are very slightly lower, but almost no different. Based on the type of pitches he throws, and where he throws them I do not think that Affeldt is a 60+% GB pitcher. I think that rate is very fluky and will settle back to his career average around 50%, but he is still a very good relief pitcher at that GB rate.

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Dave Allen's other baseball work can be found at Baseball Analysts.

7 Responses to “Lots of Groundballs from Affeldt”

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  1. oldjacket says:

    I wouldn’t be surprised if it was his curveball that was getting most of the groundballs

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  2. Preston says:

    Interesting analysis, but may I point out that you might want to adjust the colors on the graph – Affeldt and Bass, as well as Moylan and Wright, are virtually indistinguishable. Even Green and Meredith are a little challenging.

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  3. Bill says:

    This stuff is why Fangraphs is great.

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  4. Cory says:

    I think investigating his curveball and its impact on his groundball rate is essential to a thorough analysis of Affeldt since his curveball is one the biggest and best in the majors. He does a particularly good job of locating that curveball with hard, late bite towards the backfoot of a righthander.

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  5. Nibbler says:

    Yeah, I don’t think this is really an accurate analysis when you’re completely ignoring his best pitch, which, being a breaking ball, is sure to result in many groundballs.

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  6. haverecords says:

    As others have said above, and from memory of watching most of his outings this year, the curve is essential to any analysis on this. Its a filthy, big curve, at its nastiest, and, when not as nasty, it isn’t as big, but its is late.

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  7. SharksRog says:

    I’m glad you’re checking out the effect of Affeldt’s breaking pitch on his ground balls. When I saw the title of the article I was expecting the article to say that it was indeed Jeremy’s sharp breaking ball that was generating most of the ground balls.

    Affeldt has really been nails lately.

    Another off-season acquisition, Justin Miller, was signed to a minor-league contract even though his major league performance appeared to be rather solid. Miller has been the Giants’ garbage man and the last I saw had appeared in only five winning games out of 20. But his pitching has been excellent.

    As I am posting this, Miller has replaced an injured Matt Cain and thus far is mimicking Jonathan Sanchez’s hitless outing last night and Tim Lincecum’s first six no-hit ininings the previous inning. Think the Padres are having a tough time hitting. ;)

    Cain was hit on the elbow with a hard-hit ball up the middle. He lobbied to stay in the game, but when his first warmup throw went well over catcher Eli Whitesdie’s head, the Giants immediately went to Miller as a protective measure.

    The Giants have had some unexpected surprises this season, but in terms of rags to riches, the biggest may have been Miller. Most ignored Justin’s signing, and Miller didn’t make the big league team until fellow reliever Joey Martinez was beaned with a line drive and suffered a concussion that still has him pitching rehab assignments.

    Awful result for Martinez, but a great break (almost literally, since Martinez suffered a skull fracture) for Miller. And Justin has certainly taken advantage.

    Miller is now being replaced after pitching 3.1 scoreless innings, lowering his ERA to 1.98. In his previous performance he gave up a run in his second inning, but in his first came in with the bases loaded and no outs, and yielded only one run on a double play and a ground out.

    So Affeldt has been the Giants’ best off-season acquisition and Juan Uribe is another guy who has overperformed as a minor-league signee, but Miller probaby gets the award as the least-known Giant who has given excellent perfomance.

    Even with a sub-2.00 ERA, I’m not sure most baseball fans know who Justin Miller is. I’m guessing opposing batters do though.

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