A link in Thursday's Mug led me to this story at The Junkball Blues. The basic point is that Manny Parra throws his fastball fewer times than almost all other hard-throwing left-handed starting pitchers. Manny Parra also had a good strikeout rate and a worse-than-average walk rate last year. Logically, it would seem that if Parra threw his fastball more than the about 56% of the time he did last year, his walk rate might go down and he might become a better overall pitcher.

I must credit Lookout Landing with getting me thinking more about fastballs and pitch selection. This post outlines how Felix Hernandez's fastball was overused in 2008, and this one suggests that Hernandez not only was a better pitcher when he threw fewer fastballs, but his off-speed pitches were more effective when mixed with about 55% of fastballs-- differing from convential wisdom, which says that establishing a fastball helps off-speed pitches. 

I do not have the capability to split up Parra's starts the way Lookout Landing did, but I can look into his pitches using Josh Kalk's (dixieflatline) Pitch f/x tool. It has done some strange things in the past, so take everything I say here with a disclaimer. I am pretty confident in the results for Parra, however-- I have cross-checked some things with Fangraphs and Stat-Corner, and things seem to match up.

I assume the corrections used on Parra's player card at Josh's site are not used in the tool, so I did two things with the data. First, the tool separates fastballs into "fastballs" and what the algorithim calls a "splitter". Both average velocities are around 92. I combined the two pitches into "fastball", together these two pitches were thrown about 56% of the time, which matches up with Fangraphs and Parra's player card. I combined the actual splitter and changeup into a category; though the pitches are different they have similar movement and velocity, and as I said I am generalizing here. So the pitches are separated into three categories: fastballs, changes/splitters, and curves.

So should Parra throw his fastball more? Let us move on to some data. Here are the three categories of pitches. Check out the data and see if you draw the same conclusions I do. Please consider my disclaimer about the Pitch f/x tool and the sample of only 1 year.  Click for a larger version.

It would be helpful to provide some context for these numbers. Research from Lookout Landing reveals that the league average is about a 5.3% swing and miss percentage on fastballs. Parra's fastball is good, and he seems to get a lot of groundballs from using it, but batters are able to make contact with it. Compare Parra's fastball with the top lefty in terms of fastballs thrown percentage on the Junkball Blues list, Jonathan Sanchez. He threw his fastball 72% of the time in 2008, and got away with it because he was fifth in the league by drawing swinging strikes 9.1% of the time he threw it.  

The other data in the chart should be considered, too. The strike rate is the amount of total pitches of that type that went for strikes, including foul balls, outs in play, and hits-- so really it is the ((total pitches- called balls)/total pitches). The fastball was a strike more often than the other two, but not by as significant of a margin as you might expect. The next column is the percentage of swings that missed a pitch-- so this excludes all balls. When a batter decided to swing at a fastball, they made contact about 90% of the time, when they decided to swing at a curve, they only mad e contact about 75% of the time.

The last column is simply the total hits off of a type of pitch divided by the total pitches of that type thrown. Manny threw 1591 fastballs last year and gave up 116 hits off of that pitch. That was the highest percentage of hits against any of the three types of pitches.

So, to review, Parra's fastball gets put in play much more than his other pitches, is just a bit more likely to be a strike than the other two pitches, and last year went for a hit more often than his other two pitches. If you looked at the chart without any preconceived notions, you would probably reccomend that Parra throw his split/change and curve much more often. Of course, baseball does not work that way-- a pitcher has to establish his fastball before being able to trick batters into swinging at breaking pitches.

I think Parra's balance of about 55%-45% fastball:offspeed pitch ratio is quite good right now, and I see little evidence to prove that throwing his fastball more would result in fewer walks (and it could well result in fewer strikeouts and more hits, things we definitely do not want).

Parra is a good pitcher already who could develop into an excellent one if he improves his command to the 2-3 BB/9 he averaged in the minor leagues. But I do not think throwing his fastball more would help this process, based on the data available right now.

Resources: Pitch F/X tool query, so you can see for yourself the data I am working with.