What's wrong with St. Louis Cardinals closer Trevor Rosenthal?

The St. Louis Cardinals took the slimmest of leads into the ninth inning of NLCS Game 2 when manager Mike Matheny turned to closer Trevor Rosenthal. Things got hairy quickly. Rosenthal allowed two baserunners and ultimately blew the lead on a two-out, full-count fastball he bounced in front of home plate that handcuffed backup catcher Tony Cruz and allowed Giants pinch-runner Matt Duffy to dash home madly from second base.

That was Rosenthal's final batter. With the save blown, Matheny gave Rosenthal the hook and brought in sinkerballer Seth Maness to put out the closer-ignited blaze of a San Francisco rally. Maness induced a groundout and the rest is history.

After the game, Matheny fielded questions about Rosenthal's status as the closer. Matheny stayed loyal to Rosenthal, the man he has anointed as closer. If a situation occurs in NLCS Game 3 that Matheny feels requires a closer to pitch, the reliever he calls upon will be Rosenthal. Given Matheny's loyalty to players and adherence to roles, this isn't surprising in the least. Derrick Goold's excellent St. Louis Post-Dispatch article on Matheny's high usage rate of relievers in the closer job provides a window into the manager's mindset toward the role:

"Closers are closers. And they go out and close the game, and if something comes up they push through and still do it. You’re talking about a couple guys (Salas and Mujica) who were fighting injuries, whether they were silent or vocal about them. Those things dictate how it goes at the end of a season, too."

In Goold's article, Matheny points to Rosenthal's save percentage as evidence of how good he had been during the 2014 season as a closer. Rosenthal notched 45 saves in 51 opportunities for an 88.2% save rate. Not too shabby. But the ninth inning with the Cards leading in 2014 has been more rollercoaster than Sunday drive despite whatever Rosenthal's save percentage might be.

Concerns started in the season's opening weeks. Rosenthal, who often hit triple digits on the radar gun in 2013, didn't have the zip on his fastball fans had grown accustomed to seeing. But Rosenthal's fastball velocity crept upward as the season progressed. Come September, Rosenthal's fastball was averaging 98.84 mph, per Brooks Baseball, and it has averaged 99.24 mph so far in October. Velocity isn't the problem anymore. Much more concerning is Rosenthal's control.

The flamethrower has never been a finesse pitcher. Rosenthal sends his fastball homeward without much intent to paint the black of the plate. This year that approach has led to walks. In 2013, Rosenthal walked 6.4% of opposing batsmen. Rosenthal saw his walk rate more than double to 13.6% in 2014. His ERA jumped from 2.63 to 3.20; his FIP increased from 1.91 to 2.99. Unfortunately, this all can't be attributed to mud from the mound getting caked in his Nike cleats. Clearly, Rosenthal's control is worse this year than last. Or is it?

Using the Pitchf/x plate discipline information at Fangraphs, we can get data on how many pitches Rosenthal is throwing in the strike zone (Zone%). In 2013, Rosenthal threw 51.4% of his offerings in the strike zone. This year, he's thrown 50.0% of his pitches in the zone. That a decrease, but a small does not account for the more than doubling of Rosenthal's walk rate. Furthermore, Rosenthal is throwing more pitches in the strike zone this year than the MLB average of 48.8%. So why would his walk rate be so much higher than the MLB pitcher walk rate of 7.6%?

Rosenthal is digging himself in a hole more this year. In 2013, Rosenthal pumped a first-pitch strike 63.3% of this time—a healthy rate given that the league average is typically a touch over 60%. The righty has thrown first-pitch strikes just 56.5% of the time this season, well below average.

Additionally, opposing batters are swinging less often against Rosenthal. Per the Pitchf/x data, Rosenthal had a batter swing at one of his offerings 50.9% of the time in 2013 compared to 47.2% of the time this season. In particular, opposiing hitters aren't chasing pitches out of the zone: Rosenthal's O-Swing% fell from 33.6% in 2013 to 29.0% in 2014. Thus, the closer's O-Swing% went from comfortably above the MLB average rate of 29.7% in 2013 to a bit below the average of 30.1% in 2014.

What can Rosenthal do? Get on top with a first-pitch strike. A batter who is ahead in the account is less likely to expand his zone than he is down 0-1 to a reliever who can hit triple digits on the radar gun. In order to induce more swings, Rosenthal needs to fire more first-pitch strikes.