Guillermo Mota & Inherited Runs

During Clayton Kershaw's near no-hitter, on May 17 in Florida, Guillermo Mota relieved Kershaw after Cody Ross doubled to lead off the eighth inning with the Marlins' first hit.  Mota allowed Ross to score, and later allowed a grand slam to Ross.  The Dodgers were up big at the time, and the Dodgers still won going away, 12-5, but they had a problem on their hands with Mota.  They paid him $2.35 million to be a veteran in a bullpen full of young arms, and he was clearly the worst pitcher of the bunch.

After that game, Mota's ERA was a glaring 9.00 (15 runs in 15 innings) and opposing batters were torching him to the tune of .355/.449/.565.  However, help was on the way, in the form of catcher Brad Ausmus, who caught Mota that Sunday in Miami.  As chronicled by Mike Scioscia's Tragic Illness, Ausmus advised Mota to hide the ball in his delivery like he used to do, and after working with Rick Honeycutt to do so, Mota has been a changed man ever since.  From May 17 to present, here are Mota's numbers:

I'd call that quite an improvement.  The only run Mota has allowed since Miami was a go-ahead (and eventual game-winning) home run to Juan Rivera in Anaheim, but he really has been amazing for two solid months.  Part of the improvement is luck:  Mota's batting average on ball in play (BABIP) was .345 through May 17, and has been a minuscule .162 since.  The National League BABIP is .296.  So, in truth, Guillermo Mota probably falls somewhere in between horrible and amazing.

But just how amazing has Mota been during his hot streak?  After all, he has allowed nine of 21 inherited runners to score since May 17.  For example, on Friday night, Mota entered the game after Randy Wolf loaded the bases with nobody out, and Mota allowed two runs to score.  Those nine runs don't count against his ERA, but should they?  Thanks to the amazing Baseball Prospectus, we can see the run expectancy for each inning, depending on the base-out situation.  For instance, if a team has runners on first and third with one out, it is expected (based on actual play-by-play data this season) to score about 1.42 runs the remainder of the inning, on average.  We can use this to examine each of the last 11 games Mota has entered the game with runners on base, to analyze his effectiveness:

Even though Mota has allowed 43% of inherited runners to score during his hot streak, he has still saved runs.  In only two of his last 11 such appearances has Mota allowed more runs than he "should" have.  Mota has taken on an increased role in the bullpen over the last month or so, appearing in higher-leverage situations.  It looks like he has earned it.