ok, i'll play along; braden looper, starting pitcher. fine. disbelief hereby suspended. should it come to pass, how unusual would the conversion be?
keep in mind, this wouldn't be the typical reliever-to-starter trajectory. you couldn't compare it to, say, curt schilling's --- schilling made 100 relief appearances at the beginning of his big-league career, but he'd been a starter all the way up the minor-league ladder, making 100+ starts. looper made 12, none above class A. on the same basis, derek lowe is another non-precedent; although he made nearly 300 big-league relief appearances before becoming a full-time starter (and even led the league in saves one year), lowe spent 7 years in minor-league rotations, starting at every level. conversions of that type are fairly common; johan santana and francisco liriano both took that path, and adam wainwright likely will join their ranks in 2007. but looper isn't a starting pitcher who'll be returning to his accustomed role after a few years' holiday in the bullpen; he's a pure reliever who hasn't started a game in nearly a decade, at any level --- he has made 571 major-league relief appearances and 0 major-league starts.
so the question is, how many guys appeared primarily in relief in the minor leagues, and exclusively so upon reaching the majors --- and then became starting pitchers? in two hours of trolling on baseball-reference.com and the baseball cube, i only found a few such careers that even remotely fit that description.
one belongs to byung-hyun kim, who after an abbreviated minor-league career made 236 relief appearances in his first five major-league seasons. like looper he became a closer, but his two blown saves in the 2001 world series tainted him forever; he closed for another couple of seasons but never commanded much trust. in 2003 he made 12 starts and was pretty good in the role (3.38 era, 1.194 whip); he spent most of 2004 in the minors as a starting pitcher, then resurfaced with the rockies in 2005-06 as a so-so starting pitcher. in 65 career starts, he is 17-28 with a 4.81 era.
another somewhat comparable case is omar daal's. like looper, he began his minor-league career as a starter but switched to relief as he moved up the chain; above rookie ball, he made 62 appearances out of the bullpen, vs only 14 starts. for his first five years in the majors, daal toiled in the most specialized role in baseball, LOOGY (ie, "left-handed one-out guy"); wasn't particularly good at it, but a left-hander can always find work. his first 156 major-league appearances came in relief; in september 1996, the end of daal's fourth year in the majors, felipe alou gave him six starts, and daal went 2-3 with a 5.18 era. he returned to the bullpen in 1997 and was beyond awful, posting a 9.15 era in 39 games. that september (now pitching for toronto) he returned to the rotation and pitched very well in 3 starts. the diamondbacks took him in the expansion draft, and he made 23 starts for them in 1998 and posted the national league's 5th-best era at 2.88. the following year he went 16-9 and was the #2 starter on a 100-win team. he stunk in 2000 --- 4-19 record, 6.14 era --- but bounced back the next couple of years to pitch at a league-average level.
then there's charlie hough, who made 78 starts in the minors but converted to full-time bullpen work at triple A; 154 of his last 160 minor-league games were in relief. he then spent 9 years as a big-league reliever; picked up 23 starts along the way but was waved in 400+ times out of the pen. at age 34, he became a regular member of a rotation for the first time in 13 years --- and he thrived. for the next seven seasons he was a rock-solid starter, winning between 14 and 18 games a season with better-than-average eras. a knuckleballer, hough pitched until age 46, long enough to win 174 games as a starting pitcher.
because he threw a gimmick pitch, hough doesn't provide a useful precedent imho; nor does wilbur wood, who became a great starting pitcher after 350 or so relief appearances. various other guys kinda sorta fit the profile --- ron villone, bob stanley, scott garrelts, and jeff brantley all took shots at the rotation after lengthy stints as bullpen specialists. one of dave duncan's success stories, kent bottenfield, has been touted as a precedent by some people, but his case isn't comparable; bottenfield was a starting pitcher throughout the minors and reached the big leagues as a starter. he was only three years removed from rotation duty when duncan returned him there in 1998.
looper's predecessor in the stl bullpen, julian tavarez, provides an intriguing comparison. he has gone back and forth between roles his whole career --- made 80+ starts in minors and started 8 of his first 9 big-league games, but then switched to relief and spent 5 1/2 seasons in the role, making 338 appearances out of the pen. the rockies converted tavarez back into a starter in july 2000, and he did rather well for a season and a half: 15-12 record, 4.12 era, 1.45 whip, excellent numbers for a coors field pitcher. he then went back to bullpen for another 250 appearances before winding up in the boston rotation last september. he pitched very well in six starts, so much so that The Hardball Times declared "the Red Sox front office would be smart to let him battle for a slot in the rotation in Spring Training."
that was before the sox signed matsuzuka, but still . . . . . those guys at Hardball Times are pretty smart. you don't suppose this could actually work? sure it could; sure. i can see it: looper wins 20 games, and rick ankiel hits 25 homers as the starting right fielder, and the cards repeat. when eckstein's contract runs out after 2007, anthony reyes takes over at shortstop; when edmonds retires, adam ottavino is the new centerfielder.
you just gotta think outside the box . . . .