May 14, 2013 at 5:50 pm

Kurt Mensching

Whether Drew Smyly belongs in Tigers' bullpen or rotation comes down to leverage

Thereís no doubt Drew Smylyís move to the bullpen has been a successful one, but has it actually been a valuable one? Donít confuse the two. (Elizabeth Conley/Detroit News)

One common refrain states Drew Smyly is too valuable in the Tigers' bullpen to even think about moving him into the starting rotation in place of Rick Porcello.

It's an easy debate to build: With 23.1 innings pitched through Sunday's games, the left-hander has spent nearly as much time on the mound as Porcello, and he's pitched in a few tight situations this year as well. Smyly also has a 1.93 ERA and had struck out more than a batter per inning, both impressive figures.

There's no doubt Smyly's move to the bullpen has been a successful one, but has it actually been a valuable one? Don't confuse the two.

True value

Eating innings and keeping runs off the board does have some value. But let's be clear: Smyly's scoreless 5.2 innings on the mound April 20 after his team trailed 9-0 in the second inning was not nearly as useful to the team as pitching in extra innings a day later would have been.

Smyly's too good to waste in lost causes or mop-up duty, yet more often than not that's where he sees the action.

In his last four appearances, Smyly has entered the game when his team trailed three times, most recently with it down by three runs. He also entered a game where his team led 6-1.

Before stepping into the nine-run deficit in April, Smyly's role was more important. Each of those four games, he was handed a lead to protect and in all but one game did he go multiple innings while doing so.

That's the way Tigers manager Jim Leyland needs to continue using him if we're to actually accept the argument Smyly's most valuable position with the team is in the bullpen.

Checking the index

There's a stat that can help take what our gut tells us about the importance of a situation in a game and turn it into a number. That stat is called leverage index.

Created by Tom Tango, leverage index uses the inning, score, outs and position of any runners on the bases to put a weight to each possible situation in a game.

Intuitively, you know a low-leverage situation can be found earlier in a game, or in a game one team leads by a substantial margin over the other.

A relief pitcher entering a game with no runners on the bases does not have as tense a moment as one entering with bases loaded.

A visiting team holding a one-run lead with two outs in the bottom of the ninth inning or extra innings is as leveraged as you could ask for: The entire game comes down to the outcome of one pitch.

You don't need a stat to tell you that, of course. Your heart is pounding in your throat. That's how you know it's a high-leverage moment.

Still, it's useful to compare just what kinds of situations relief pitchers have been thrown into.

Pegged to numbers, 0 is no leverage at all, 1 is average leverage, and anything above 2 is high leverage. (Our theoretical bottom of the ninth above ranks as 10.9 by Tango's calculations.)

The average leverage when Smyly enters a game is 1.07, according to FanGraphs.com. Seven Tigers relief pitchers enter into more-tense situations, including fellow lefties Darin Downs (1.42) and Phil Coke (1.91).

Only two games were near the high-leverage mark: April 12 in Oakland (1.91), when Smyly entered with a one-run lead in the bottom of the seventh, and April 17 in Seattle (2.07), when he entered a tie game in the bottom of the 13th.

In order for the Tigers to get the most use of their reliever, they're going to have to use Smyly more often during key moments of the game.

Only then will an argument Smyly's best place is in the bullpen carry any weight.

Kurt Mensching is the editor of Bless You Boys, a Tigers blog (blessyouboys.com). He can be reached at bybtigers@gmail.com.