Heading into spring, four/fifths of the rotation was already decided. RHP Jason Johnson, LHP Mike Maroth, RHP Jeremy Bonderman, and RHP Nate Cornejo had spots locked up based on their potential and their performance from last season. Four other pitchers came to camp hoping to nail job the final spot; LHP Nate Robertson, RHP Ariel Prieto, RHP Esteban Yan and RHP Shane Loux. Both Prieto and Loux pitched themselves out of the competition, while RHP Gary Knotts got another shot after an inconsistent run last year.
Over the past three days, Yan has seriously hurt his chances, while Robertson helped himself immensely. Yan was roughed up in a start against the Reds (6 ER in 2.2 IP), while Robertson was very impressive against the Braves (4 IP, 5 H, 1 ER, 1 BB, 6 K's). Knotts gets his chance to show what he can do this afternoon against St. Louis.
The possibility remains that the Tigers still might fill the role with someone outside of the organization – Pedro Astacio remains a free agent, and teams like Los Angeles and Anaheim are looking to move some of their pitching. But until a move happens, the Tigers will be forced to take one of the three left still fighting for the spot.
Robertson and Knotts have both had a chance and been extremely inconsistent, and there's no telling whether or not either can give the Tigers consistent production in the fifth slot over the course of the season. Yan, up until his last performance, looked to be the front-runner, but he hasn't pitched an entire season as a starter in years and there's no telling whether or not he'll be able to hold up.
So, as of now, the Tigers appear to be looking at a situation of who can do the least harm as opposed to who can help the most. For a team looking for significant improvement, that's probably not the best situation. It remains to be seen whether or not the Tigers will try and add another starter, but if they don't, they can only hope one of the three can overcome what's been keeping them from solid production and give the Tigers a respectable fifth starter.