What is Trevor Rosenthal’s long-term role with the St. Louis Cardinals?

For 2014, the answer’s easy. Rosenthal will lock down the ninth. After securing the closer job late last season, he emerged as a late-inning force in the Cards’ playoff run.

But for 2015 and beyond, all bets are off. Or at least they should be. While Rosenthal enjoys closing, he’s stated in the past his desire to start. 

Early in spring training, Rosenthal talked about his situation with Rick Hummel of the St. Louis Post-Dispatch.

Starting would be a different challenge. Coming into the organization, I always kind of envisioned that being the end result.

The last time Rosenthal started, he was 8-6 with a 2.78 ERA in 94 innings for Double-A Springfield in 2012. Then he got the call to Triple-A, posting a 4.20 ERA in three starts.

In 2011, Rosenthal had his first taste as a regular in the starting rotation. He struck out 133 in 120 1/3 innings for Low-A Quad Cities. The 4.11 ERA wasn’t overly impressive until you factor in the shoddy defense behind him. According to Baseball Instinct, his FIP (Fielding Independent Pitching) rate was 3.22.

Rosenthal had struggled in August, as the 7.12 ERA that month hinted at the strains of a workload over a full season. But he impressed the Cards’ front office during spring training in 2012, prompting St. Louis to bump its flame-throwing prospect to the Texas League.

The repertoire is there for Rosenthal to succeed in the rotation. The high-90s fastball is his calling card. The natural sinking action creates plenty of ground balls. The power slider is a great complement. And while he doesn’t use the changeup often in his current role, it was an improved offering during his time in the minors.

In a short period of time, Rosenthal has emerged as an elite closer. And considering the club’s starting depth, it’s a no-brainer to keep him planted in the ninth inning this season. However, pitchers with this type of arm don’t grow on trees. It would behoove the Cardinals to find out if he could translate his success to the rotation.

Winning in today’s game has become more reliant on a strong bullpen. Still, 200 quality innings from a starter offers more value than 70 innings of relief, no matter how dominant.

Jason Motte’s return from Tommy John surgery could factor in Rosenthal’s future. He established himself as a stopper by saving 42 games for the Cardinals in 2012 after excelling in October for a World Series winner in 2011.

Motte’s a free agent after the season. It’s doubtful he’d re-up with the Redbirds as a set-up man knowing the money available on the open market.

Every year, the role is a revolving door. Teams are finding success without a mainstay in place.

Tampa Bay has won 90 or more games in four straight seasons using three different closers.

Atlanta’s Craig Kimbrel is the only pitcher to save at least 30 games for the same team the last three seasons. The four teams in the last two Fall Classics each utilized different closers from the pitchers who started the season.

Veteran reliever Edward Mujica had four career saves before knocking out 37 for the Redbirds last season.

Then there’s the money factor.

Teams are increasingly reluctant to pay big dollars for closers. The Orioles decided to trade Jim Johnson, who had back-to-back 50-save seasons, rather than pay the arbitration-eligible right-hander a salary close to $10 million.

Rosenthal may never cash in on big-time starter money like Clayton Kershaw. But even average big-league starters are garnering $15 million or more per season in the current market.

Kimbrel, arguably the game’s top stopper, signed a four-year, $42 million extension. His biggest payday will come in 2017 when he’ll make $13 million. The Cubs are paying Edwin Jackson $11 million, and his ERA was barely under 5.00 last season.

I’m sure Rosenthal is well aware of the discrepancy.

It’s understandable to ask where Rosenthal fits into a St. Louis rotation filled with established young arms and a bevy of intriguing prospects on the way.

Adam Wainwright is signed through 2018. Of Lance Lynn, Michael Wacha and Shelby Miller, Lynn is the closest to free agency, but that won’t come until 2018. Carlos Martinez could be ready to graduate to the rotation. Jaime Garcia, Tyler Lyons, Joe Kelly, Marco Gonzales and Tim Cooney also are in the mix.

So why mess with a good thing?

Rosenthal could fizzle as a starter. He could get injured. Maybe he’d tire after a few innings, lose velocity. Those issues contributed to former Cardinals reliever Todd Worrell moving to the bullpen in the ‘80s. He excelled there.

Rosenthal already is thriving as a closer. But just imagine what he could become as a starter.

You’ll never know until you try.

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