I blame Johan Santana. Though Santana was always groomed as a starter and although he threw as many as 160 innings in his final year in the minors, the Twins bounced him back and forth between relieving and starting for each of his first four seasons in the majors. When he finally entered the rotation full-time at the age of 24, he rewarded the Twins “strategy” by giving them four seasons during which he averaged 228 IP, 18 W, 2.89 ERA, 0.99 WHIP, 9.7 K/9, and 6.3 rWAR. Over that stretch he won two Cy Youngs, never finished lower than fifth in the voting, and made three excellent postseason starts (although the Twins never made it out of the first round).
Following Santana, the Twins made this “variable-role development” a common organizational model for introducing top prospects. Carlos Silva spent two full seasons in the ‘pen before graduating to the rotation at the age of 24. Francisco Liriano spent his first full season, 2006, being shuffled back and forth on much the same schedule as Santana (and spent the following season rehabbing from Tommy John surgery). Former first-rounder, Glen Perkins, started his Twins career in the bullpen and has since been moved back to it. Boof Bonser, Kevin Slowey, Brian Duensing, and the supposed fruit of the Santana trade, Anthony Swarzak, have all done time in both the Minnesota ‘pen and the Twins rotation. While the jury may still be out on several of them, it’s safe to say that, much like the Yankees, the Twins are now far more renowned for grooming relievers than starters.
The second greatest bullpen-to-starter success story of the last decade is that of Adam Wainwright. Wainwright was promoted as a reliever in 2006, at the age of 24. He was excellent in relief, famously closing out the Cardinals World Series win over the Tigers, and was converted to a starter the following spring. He looked like a perennial Cy Young candidate until he missed all of 2011.
After Santana and Wainwright, the evidence justifying variable-role development gets really thin. Zack Greinke spent much of 2007 in the bullpen, when he was still in his early 20s, but Kansas City only resorted to making him a reliever as a means of working him back from the emotional issues that cost him all of 2006. Last year, Alexi Ogando (who reached the majors somewhat late, at age 26) made the All-Star team for Texas in his first season as a starter. However, he fell apart after the break (5.11 ERA in last 13 games) and appears to be headed back to the bullpen in 2012.
As you can see, there aren’t that many success stories, but that doesn’t mean teams have given up on the strategy. This season could be critical to its long-term viability. The Red Sox will likely begin the year with either Bard or Alfredo Aceves in the rotation. Both were starters in the minors and have not been since. Cory Luebke in San Diego and Hector Noesi in Seattle, both having opened their careers as relievers, will move to being full-time starters. The Rangers rotation will feature three players under the age of 27 – Neftali Feliz, Derek Holland, and Matt Harrison – who spent substantial portions of their early careers in the bullpen. Hughes, Masterson, Brandon McCarthy, and Brandon Morrow head a group of variable-role graduates with the potential to shrug off previous inadequacies now that they’ve reached their late twenties. Will there be another Santana or Wainwright among this group? Maybe, maybe not. But so long as they aren’t all Yusmeiro Petit‘s, it will probably be considered a successful year for variable-role development.