I thought it would be interesting to do a quick study on the best and worst batting and pitching performances so far this year. A quick way to measure the value of a performance is WPA, which is Win Probability Added*. It sums the value of each play made by a certain player in a game. For a quick example, say that Vernon Wells comes up in an inning with the Jays chance of winning at 45% (e.g. down by one in the middle innings). If Wells hits a home run, and the chance of winning increases to 50%, then the value of the home run is 5%. If you add up (or subtract) the total changes in chances of winning the games, you will get WPA. It is a little confusing at first, but it is an extremely useful (if not the most useful) statistic for measuring a player's contribution to winning individual games or his value over a season or career.
*Quick note: I am using the WPA from Baseball-Reference, which may differ from that of Bill James or FanGraphs as each site has a slightly different WPA formula, but all numbers end up very close
The first thing we are going to look at is the best performances for Jays hitters. This shows the the most valuable game so far this year by a Jays hitter was Adam Lind against the Cleveland Indians on May 5. The Jays won the game 5-4, as Lind hit a 2-run home run with 2 outs in the 9th inning and the Jays down by 1 run. For the game, he went 2 for 4 with a walk, a run, and 2 RBIs. FanGraphs shows that the home run had a WPA value of .724, as the probability of the Jays winning the game went from 8% to 80.5%. That game by Adam Lind, and especially the home run, is the most valuable hitting performance by any Jays player so far this year.
The next thing to look at is the best performance by a Jays pitcher. Any guesses on what the result might be? Yep, it was Brandon Morrow's gem on Sunday against the Rays that had the highest WPA, which corresponds to what I described here this week. One of the biggest reasons why it was so high was because of aLI, or the Average Leverage Index. aLI measures the average pressure that a player will face in each situation, with 1 being average pressure, under 1 being low pressure, and above 1 being high pressure. (An interesting sidenote is that the top 12 best pitching performances are from starters, while we will see that 6 of the 7 worst pitching performances are from relievers. This has a lot to do with aLI, as the best performances are usually when pitchers pitch 8 or 9 shutout innings in a close ball game, while the worst performances are usually when relievers enter a close game and get lit up.) Morrow had an aLI of 1.454, which was also higher than any of the other performances on the list. A big reason why it was so high was because the Jays were only winning 1-0 throughout the entire game, so Morrow could not take any innings off because of a big lead, but had to pitch hard the entire game.
Now, the flip side. We have looked at the best performances of this year so far, now we need to look at the worst. First up, the worst hitting performances so far. Alex Gonzalez's June 23 game against St. Louis comes in as the worst performance so far with a WPA of -0.376. Gonzalez went 0 for 3 with a walk, and 2 double plays grounded into. Both double plays came after leadoff singles by Vernon Wells (in the 4th and 9th innings), and since the Jays ended up with a 1-0 loss, any run would have helped a lot. The 9th inning double play was the play with the largest change in WPA for the Jays, as the Jays went from having a 34.2% chance of winning to only a 4.9% chance of winning (WPA of -0.294). That play, along with his hitless night, gives him the top spot in the worst hitting performance of this year.
Finally, we are going to look at the worst pitching performance of this year. I don't know about you, but when I think about bad pitching so far this year, one name pops into my head: Kevin Gregg. Gregg has gotten a lot of saves (25 so far), but has also blown a couple (4 so far, resulting in an 86% save percentage). But to me, it always seems as if he pitches well under the least pressure, that is, if he comes into the 9th with a 3-run lead against the Orioles, he will always get the save, but if he comes into the 9th with a 1-run lead on the Yankees, he will blow it. And when we take a look at the leaderboard, Gregg's name is all over it. He actually holds the top 3 spots for worst pitching performances, but the one that takes the cake is his performance against Seattle on May 20. He came in with a 3-1 lead, and then: single, single, walk, walk, sac fly, single, game over. Gregg's line: 0.1 IP, 3 H, 2 BB, 3 ER, BS, and L. He threw 25 pitches, only 12 for strikes, and his WPA was an astoundingly bad -0.905, as the Jays had over a 90% chance of winning when he entered, and ended up losing.
There are your best and worst performances so far in 2010. An interesting note is that all performances came in 1-run games, with the games winning 5-4 and 1-0, and losing 1-0 and 4-3 in the respective order of the performances. This again has to do with aLI. The higher the aLI, the higher the probability that a single play (or a couple plays in a row) can swing the entire outcome of the game. And although we measured everything in terms of WPA, I believe that the results we have come up with should pass the "gut-check"; that is, if you were to eyeball some of the best and worst performances so far this year, many of these performances would be at the very top (or very bottom).
We will check back on this post at the end of the year, to find out if the results will still be the best and worst performances after 162 games. Also, tomorrow I will be working on a post similar to this one, for the best and worst performances by opposing players when they are facing the Jays. I would not be surprised if many of the same games we looked at today will be involved tomorrow.
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