A Look at St. Louis Cardinals Closer Edward Mujica's Arm 'Fatigue'

On Sunday, Jenifer Langosch of MLB.com broke the news that St. Louis Cardinals closer Edward Mujica had been unavailable to pitch during the club's weekend series at Wrigley Field. The Redbirds did not face a save situation against the Cubs but, if they had, rookie flamethrower Trevor Rosenthal would have gotten the call. Langosch reports that the reason for Mujica's unavailability was "arm fatigue."

Langosch quotes Mujica as follows:

"I was tired," Mujica said. "I talked to [Matheny], we have good communication. I said, 'Mike, I feel, not sore, but just a little tired.' I prepare for one inning, maybe four or five outs, but to have two innings three times in a row [was a change]. It was good to have these three days [off]."

Matheny's usage of Mujica of late has been somewhat strange. During the Cardinals' 7-game losing streak, Matheny did not use the club's closer once. However, Mujica did pitch the ninth inning of the Cards' losing-streak-breaking 13-0 win over Pittsburgh on August 1. As the Cardinals faded during a brutal stretch of their schedule that saw them play 22 games over 21 days without an off-day, Matheny leaned on his closer.

On August 11 against Chicago, Mujica notched a six-out save, throwing 30 pitches over two innings of work. In the series against the Pirates at Busch, Matheny used Mujica in two more two-inning appearances. Mujica handled the ninth and tenth innings in the club's 4-3 win on August 13, needing only 17 pitches to record six outs. Then, on August 15, Mujica threw 24 pitches over the tenth and eleventh innings, helping maintain a tie game that el Birdos eventually won in the bottom of the twelfth inning.

Prior to last week, Mujica had one appearance in 2013 that was two innings in length--on June 4 versus the Diamondbacks. The most pitches Mujica had thrown during a 2013 appearance before last week was 22 against Houston on July 10. Matheny rode Mujica comparatively hard last week: five days, three appearances, six innings, and 71 pitches. No wonder Mujica was fatigued.

Using the Pitch F/X data at the indispensable (and recently redesigned) BrooksBaseball.net, we know that Mujica's four-seam fastball has had an average velocity of 93.08 mph from Opening Day 2007 through August 15, 2013. (Pitch F/X is not available for Mujica's debut big-league season of 2006.) Last year, Mujica's four-seamer averaged 92.65 mph. In 2013, Mujica has pumped his fastball in at an average speed of 92.82 mph.

On August 11, Mujica was throwing darts. He threw his four-seamer 16 times out of 30 pitches and averaged 93.48 mph with the pitch. On August 13, Mujica did not throw a single fastball. All 16 of the righthander's offerings to the Pirates were his Nintendo split-change. Mujica changed things up a little bit against Pittsburgh on August 15. Of the 24 pitches Mujica threw, 17 were split-changes; 7 were four-seam fastballs. Mujica's averaged 91.76 mph on those fastballs. Mujica's average fastball speed on August 15 was 1.06 mph below his 2013 overall average and 1.72 mph slower than the average radar reading on his fastball from August 11.

We must keep in mind that fastball speed goes up and down for every pitcher from one game to the next. The drop in Mujica's average fastball speed on August 15 does not conclusively prove he was tired. But, when the manager and player are saying the player was held out of action because of fatigue and the data shows a drop in fastball speed, it's fairly persuasive evidence.

While Mujica's tired arm is undoubtedly concerning, it's not the end of the world. Langosch reports the following silver lining to the story of Mujica's fatigue:

Both Mujica and Matheny were optimistic that Mujica would feel fresh enough to pitch, if needed, on Monday in Milwaukee.

Of course, Matheny also admitted to lying to reporters on Sunday morning about Mujica's availability so that he would have a competitive advantage against the Cubs that afternoon, so take Matheny's articulated optimism with as much salt as you see fit.

Even with Matheny and Mujica's optimism that he will be rested and fresh as soon as today, this is a situation worth monitoring. When Mujica next takes the ball for the Cardinals, I'll be paying attention to the radar readings. Hopefully Mujica's fastball does not give us reason to think he is still fatigued.