A PITCHf/x Look at Gio Gonzalez

After being acquired from the Washington Nationals, lefty Gio Gonzalez has been off to the best start of his career. Before this year Gonzalez was a solid pitcher and in 2010 he began to take off. During that time he has posted fWARs of 3.2 and 3.5 respectively. His FIP during those times was 3.78 and 3.64 which is considered above average. This year it's a whole new story, he currently has 3.1 WAR to go with an excellent, yet highly unsustainable 2.07 FIP. His 2.97 xFIP and SIERA are identical, so even if Gonzalez runs into some regression he should still remain dominant. What's the cause for the sudden change? More after the jump.

Like I mentioned, before Gio Gonzalez got to the Nationals he was a very solid pitcher. He was always known as a guy with big strikeout potential, but his number one nemesis was issuing walks. Before this season he had never averaged less than 4 walks per nine innings. This season he's managed to bring that below 4 BB/9 and is currently walking 3.61 per nine innings. With the reduced amount of walks he's also been able to bring up his strikeout total. His previous high was 9.94 strikeouts per nine innings, and that was in 2009 when he started 17 games. This season he's brought it all the way to 10.74 strikeouts per nine innings, it's highly possible that moving from the American League to the National League helped though. The NL doesn't use the DH, as you know, so he's facing batters that aren't as good as in the AL.

Let's take a look at Gonzalez's repertoire and see how he used it against left and right handed batters during the 2011 season.

Gio Gonzalez vs RHB 2011:

You can see that Gonzalez typically attacked right handed batters with either his four seam fastball, his two seam fastball or his curveball. Gonzalez's four seam fastball is +9.13 VER and 6.66 HOR, overall that's pretty straight but is has a little bit of life that comes in on right handed batters. When he used his four seam fastball he got strikes 65.2% of the time, which is a very good result. Batters also swung and missed 12% of the time, this is also known as Whiff%. His two seam fastball is +5.86 VER and +10.64 HOR meaning that it typically was down and away on right handed batters, so when they swung the bat they were reaching. With the two seam he was able to get strikes 58.4% of the time and had a Whiff% of 4.5%. His curveball is a sweeping curve that came and jammed righties. With the curve batters swung and missed 12.9% of the time and overall he managed to get strikes 57.9% of the time. He has a solid change-up against righties that had some good depth. His change-up was the pitch that got strikes the least amount of the time, it came in at 49.3% but when batters swung they missed the most out of any of his pitches. Batters managed to whiff 14.5% of the time.

If you're a visual person I have a graph that can show you what I just explained but with a picture.

We looked at what he was able to do against right handed batters last year, now let's take a look at how he fared against left handed batters.

Gio Gonzalez vs LHB 2011:

Against left handed hitters the sample size is much smaller but nonetheless we'll take a look.

He primarily uses his fastball when dealing with lefties, and it basically does the opposite of what it does when thrown against a right handed hitter. He was able to get strikes 64% of the time, while getting batters to miss 11.1% of the time. He didn't use the two seam as much but when he did he got strikes 64.4% of the time and whiffs over 5% of the time. It makes sense that his two seamer was more effective against lefties because it jammed on them. His curveball was solid against lefties, he got 53.9% of the time and whiffs 8.6% of the time. The curve went away from lefties, but it didn't quite leave them chasing. He only threw two change-ups last season against lefties so we'll avoid that all-together.

Gio Gonzalez was able to post solid results last year but this year he's brought it to a whole new level. Let's see what has helped him do so much better.

Gio Gonzalez RHB 2012:

Right away we can see that Gonzalez is using his four seam fastball a lot more against right handed batters. Overall the results are fairly similar but his two seam fastball is what's interesting. He's throwing it less than last year but he's gotten much better results so far. He's getting strikes 63% of the time, 5% more than last year. Batters are also swinging at it 4% more and are whiffing 1% more. He's getting strikes 4% less with his curveball this year but batters are whiffing about .5% more, not a big difference. Instead of using his curve as much he's been using his change-up and has also gotten better results. In the NL, batters are swinging at the curve 16% more compared to the AL. As a result he's seen his Whiff% go from 14.5% to 17.9%. He's also getting strikes 9% more of the time against righties compared to last year. He's throwing it basically where he threw it last year so the success is interesting. Like I said earlier though he's also facing worse competition in the NL.

Gio Gonzalez LHB 2012:

With his four seam fastball he's getting strikes 4% less, going from 64% to 60% but batters are whiffing 2% more of the time. It has a little more vertical movement than last year so that might have an affect. His two seamer has been really nasty against lefties though. He's getting strikes 15% more often this year, going from 64% all the way to 79%. He's also seen a 6% increase with his Whiff%. His results with his curveballs against lefties this year is essentially the same as last year. Again, he's only thrown 3 change-ups versus lefties this year.

Overall, it's no secret that Gonzalez changed something with his approach this year. He's using his two seam fastball and change-up a lot more against right handed hitters and the results have followed. Again, the switch from the AL to NL most likely has aided him but if he can keep doing his thing he should finish the season as his best to date.

Stats and graphs used are from Texas Leaguers and FanGraphs.