Thursday, December 5, 2013

Sox sign Edward Mujica, Uehara lite?

Today, December 5th 2013, the Red Sox announced a 2 year, $9.25 million contract with former Cardinal closer Edward Mujica. This comes 364 days after the Red Sox signed former Ranger reliever Koji Uehara to a one year, $4.25 million deal with a vesting option.

A quick glance at Mujica's season statistics indicate some cause for concern. First, his strikeout rate in 2013 was below average, at a rather pedestrian 6.40. For comparison, all pitchers struck out 7.57 batters per nine innings, while relievers struck out batters even more frequently (8.29 K/9). Second, Mujica's shiny ERA (2.87) masks a Fielding Independent Pitching (FIP) ERA of 3.71, precisely reliever average. Third, although Mujica recorded 37 saves in 2013, he imploded in September posting an 11.05 ERA and was a non-factor in the Cardinal's World Series run, throwing only 2 innings in the entire postseason.

However, I believe this is a solid signing for the Red Sox and Mujica could return a great value for them just as Uehara has. Why?

Just like Uehara, Mujica doesn't walk anyone

Source: FanGraphs -- Edward Mujica, Koji Uehara
In 2013, Mujica walked 0.70 batters per nine innings, the very best in baseball. Even Koji Uehara, with his impeccable control, walked 1.09 batters per nine innings. Although we shouldn't expect Mujica to repeat his sub 1.00 walk rate, this isn't out of the blue. Since 1989, when modern bullpen usage really took hold, Mujica's walk rate (1.39 BB/9) is the fourth best, trailing only the aforementioned Koji Uehara as well as Bob Tewksbury and Dennis Eckersley.

Just like Uehara, Mujica's strikeout to walk ratio is elite

Source: FanGraphs -- Edward Mujica, Koji Uehara
In 2013, Mujica's strikeout to walk ratio was 9.20, second best in baseball. Again, we're in Koji Uehara territory here, as Uehara led the way with a K:BB of an astounding 11.22. Just like with his walk rates, Mujica's career numbers put him in elite company here as well. Looking at all pitchers who have thrown 100 innings since 1989, Mujica's K:BB of 5.15 is the 4th best, only trailing Uehara, Eckersley, and Sergio Romo.

As an aside, Uehara might have the most impressive careers among modern relievers
Here are Uehara's numbers for his career, including ranks among pitchers with 100 IP since 1989:
K/9: 10.45 (36th)
K %: 30.4% (12th)
BB/9: 1.20 (1st)
BB %: 3.5% (1st)
K/BB: 8.74 (1st)

Needless to say, the Red Sox are either really lucky or brilliant to have landed one of the best relievers of the modern era for a few million a year.

Based on swinging strike rates, Mujica ought to be striking out a lot more batters
Finally, and perhaps most importantly, Mujica ought to be striking out a lot more batters. Using the model I created to examine Buchholz's 2013 improvements, which predicts K/9 based on the swinging strike rate and the percent of pitches in the zone that are swung at, Mujica's K/9 was expected to be 9.00, instead of his below average 6.40. The one caveat with those modeling results is that Mujica has consistently underperformed his expected K/9 since 2010 (8.63 K/9 expected, 7.41 actual). There may be something about Mujica that lowers his strikeout rate the model doesn't adequately capture. Even with that adjustment, we could expect Mujica's K/9 to be about 8.

Mujica fits in to the Red Sox bullpen approach of limiting walks
Tazawa, who I mentioned above, profiles similarly to both Mujica and Uehara as well - very few walks, plenty of strikeouts (9.48 K/9, 1.58 BB/9, 6.00 K/BB). With the Mujica signing, the Red Sox now have three of the top five active pitchers since 1989, and top 10 in 2013, in terms of strike outs per walk. Not bad for about $10 million per year. Add in a healthy Andrew Miller, whose astronomical strikeout rate more than makes up for a mediocre walk rate, and postseason fireman Brandon Workman, and you're looking at a dominant back end of a bullpen.

What might have been
As I perused the leader boards, a couple of names jumped out at me - Mark Melancon and Casey Fien. Both had their stints in the Red Sox organization, although I'd forgive you if you didn't remember Fien's rather brief tenure. Melancon came over in exchange for Jed Lowrie prior to the 2012 season, and had one disappointing season with the Sox before being shipped to Pittsburgh in the ill-fated Hanrahan deal. In 2013, Melancon put up the second best walk rate (sandwiched between Mujica and Uehara) and third best K/BB (behind Mujica and Uehara) while pitching in high leverage innings, albeit not closing. Fien was briefly in the organization after being claimed off of waivers from the Tigers in March of 2010. It was a move I praised at the time, thanks to his excellent minor league numbers. However, after the Red Sox claimed him, they tried to sneak him through waivers. The Blue Jays claimed him, only to waive him two weeks later. Fien resigned with the Tigers for the 2010 season, but only appeared in 2 games, followed by the Astros in 2011 where he didn't make a major league appearance. Fien appears to have settled into the Minnesota bullpen, however, and had the 8th best K/BB in 2013, at the age of 29. It took awhile, but Fien has finally established himself as a back of the bullpen arm. Given that Melancon and Fien would still be under team control had the Red Sox kept them, it is fun to imagine a bullpen going in to 2014 that would have four of the top five relievers in terms of K/BB


  1. Even more amazing is that Mujica's first strike percentage, which is the best predictor of walk rate, is 75%. That's the best in majors for players with at least 50 IP. Koji Uehara was in second at 70%.

  2. It may be a small sample size, but should we be at all concerned about Mujica's September implosion? Was it just bad luck, fatigue, a bit of both? The Cardinals were obviously not interested in keeping him, which is surprising to me considering that Rosenthal and Martinez could be moved from the bullpen to the rotation.

  3. That is a good question. I think it is hard to put too much stock in a bad month for a reliever, as those terrible September stats came in just 7 innings pitched. It is sometimes questionable to really break down any pitchers stats into monthly splits, given how small sample sizes can be, but especially so for a reliever. In the absence of any report of an injury, I'm not too worried about it. Perhaps teams are having too short of a memory there. I'm sure the Sox did their due diligence on any potential injuries (Mujica claims he's totally healthy, but it isn't as if he's going to say otherwise). If his terrible month had been April (like Greg Holland's was last year) or July, I'm not sure they're able to sign him for 2 years, $10 million.

  4. Small sample sizes, particularly with relievers, can lead to teams making poor decisions with the bullpen. Just look at the Sox and Mark Melancon two years ago. I think Bill is right not to be worried about it. The deal seems to be fairly low risk/high reward, which is a rare thing in a FA reliever contract.

  5. One additional advantage to Mujica is that his contract is quite favorable, compared to the deals other free agent relievers have signed. The most deals so far either top Mujhica's in terms of annual salary (Brian Wilson, Joe Nathan), years (Javier Lopez), or both (Joe Smith). Nathan stands apart in that group as a proven closer, but Brian Wilson threw all of 20 innings last year (including the playoffs) and neither Smith nor Lopez have any closing experience. In fact, Lopez is really a Left Handed One Out Guy (LOOGY) and can't effectively get right handed batters out (.800 OPS in 2013). Compared to all these deals, Mujica looks like a steal, even with his worrisome September.

  6. Not to mention Boone Logan (3 years, $16.5 million to Colorado). I would have picked all of those guys (Smith, Wilson, Lopez, and Logan) after Mujica.