BTF: C.J. Wilson's attempt at history

As of Sunday morning, the Rangers hold a three-game lead in the American League West. Perhaps the biggest reason is starter C.J. Wilson, who is 3-1 with a 2.55 ERA in eight starts. What makes Wilson's performance most surprising is he's a converted reliever. Before Wilson's seven scoreless innings against the Blue Jays on April 8, he hadn't started a game since August 2005. As a rookie, he went 0-5 with a 12.05 ERA as a starter and 1-2, 2.73 as a reliever, which resulted in what seemed to be a permanent move to the bullpen.

The move from the bullpen to the rotation is rarer than you think. The opposite path is far more common. Even in an age in which relief pitchers are highly valued and players such as Huston Street and Drew Storen are groomed as closers from the time they sign a professional contract, six of the 10 closers with the most saves in 2009 were converted starters.

So, exactly how rare is the move back to the bullpen?

To answer this question, I looked at all full-time relievers in baseball history. I defined a full-time reliever simply as any pitcher who pitched 90 percent of his games in relief for two seasons of at least 40 innings pitched. After narrowing history down to these players, I looked to see how many became full-time starters in the following season. Setting a fairly low bar of two-thirds of games as a starter and 80 innings pitched, only 49 pitchers made the move. After restricting it to a higher standard of 80 percent of games started, the number of pitchers dropped to 30. If Wilson can last a season in the rotation, he'll be in elite company.

Overall, the numbers for these relievers turned starters are very good. As relievers, this group of 30 had an ERA of 3.41 in the 'pen, and it rose to 3.61 in the rotation. Their K/9 went from 7.0 to 5.6, and their BB/9 dropped from 3.6 to 2.7 while starting. However, these numbers can be misleading because these conversion experiments tend to end quickly if the guy struggles in the rotation. Therefore, guys who stunk it up in the rotation never got enough innings to qualify for this study.

That said, let's check out some of the success stories.

Before the 1967 season, Wood became a full-time knuckleballer. Within four years in the White Sox's bullpen, he became the league's biggest workhorse reliever, leading the AL in games pitched for three consecutive seasons (1968 to 1970). Wood was moved to the rotation during spring training in '71, and in the next five years until a Ron LeFlore liner shattered his knee, he won 110 games and threw 1,738 innings.

As a prospect, Finley never started a game in the minors and broke into the majors solely as a reliever. In September 1987, with the Angels having just traded John Candelaria to the Mets and Kirk McCaskill shut down for the year thanks to injuries, Finley started three games with unimpressive results. The Angels lost Don Sutton and Jerry Reuss after the year and Finley stayed in the rotation with mixed results in 1988. Finley had a breakout year in 1989, going 16-9 with a 2.57 ERA, making his first All-Star Game. He never pitched another game in relief and won 195 games as a starter.

Lowe led the league in saves as the Red Sox's closer in 2000 but lost his job in 2001 when Boston acquired fireman Ugueth Urbina from the Montreal Expos. With Lowe under contract through ther 2003 season, the team decided to try him in the rotation rather than employ him as a very expensive setup man. Lowe went 21-8, 2.58 for the Sox in 2002 and finished third in the Cy Young award voting. He has won 126 games since the conversion.

People were skeptical when the Cubs decided to move Dempster to the rotation in 2008. Given that Dempster had been one of the worst closers in the league in 2006 and 2007 and had previously become a reliever in 2004 after several years of control problems as a starter, most pundits (myself included, sadly) were predicting disaster. Dempster won 17 games and finished fourth in the NL in ERA, and he has been a steady presence in the Cubs' rotation since.

So, what can we expect from C.J. Wilson going forward?

It should surprise nobody that Wilson is extremely unlikely to finish the year with an ERA anywhere near 2.55. He's pitched very well, but he got lit up by the Angels in his last start, allowing seven runs in 4 1/3 innings while allowing his first two homers of the season.

FIP (fielding independent pitching), which measures expected ERA from peripheral statistics, has Wilson's performance in 2010 as 3.53, while xFIP, which is a version of FIP that normalizes home runs as a percentage of fly balls, has Wilson's expected ERA as 4.25. It's perhaps a little disappointing, but a full-time starter with an ERA of 4.26 is extremely valuable in Arlington. The Rangers should be pleased with how their experiment has worked out so far, but it still remains to be seen how durable Wilson will turn out to be as a starter.

Dan Szymborski is editor in chief of Baseball Think Factory.