Manager Joe Maddon said all along the decision was not an easy one, due in part to Niemann's potential and his superior Spring Training work. The 6-foot-9 right-hander posted a 2.92 ERA and struck out 17 over 24 2/3 innings this spring, while Hernandez recorded a 5.33 ERA and struck out 14 over 27 innings.
But Spring Training stats aren't everything -- far from it. The Rays watched Niemann's velocity peak in the 88 mph range and wanted him to continue to build up arm strength. Maddon stopped short of saying the Rays were concerned about Niemann's dip in velocity, and he reiterated that Niemann will be a starter down the road -- "a very good one, actually" -- even if he's beginning this season as a long reliever.
"It's definitely disappointing. I felt like we presented a pretty good case and you can look at my past and know what we're capable of doing," Niemann said. "I couldn't have done anything else to put myself in a better spot. It's just where we are."
Tampa Bay has thought of Hernandez, formerly known as Fausto Carmona, as an innings-eating starting pitcher since the club signed him to a one-year, $3.25 million deal (plus incentives) in December, so he will join David Price, Jeremy Hellickson, Matt Moore and Alex Cobb in the rotation to start the season.
Hernandez will pitch three innings in a Minor League game Saturday, setting him up for his first start in the Rays' third game of the year.
Price will pitch on Opening Day against the Orioles, and he'll be followed by Hellickson on Wednesday and Hernandez on Thursday. Moore will begin the year as Tampa Bay's fourth starter, making his 2013 debut Friday against Cleveland, and Cobb will round out the rotation and make his first start on Saturday.
Maddon said lining up the rotation that way came down to the club's evaluation of which pitchers should fare the best against which teams through the first month of the season. But he also liked the idea of putting the more durable Hernandez between Hellickson and Moore, both of whom struggled to pitch deep into games last season.
"Within Matt and Jeremy, there's definitely the ability to get deeper. We've just got to draw that out of them," Maddon said. "But as you set it up, just trying to set it up in a manner that permits you to utilize your starters well ... then also being able to keep your bullpen solvent. All that stuff, you're just trying to make your best guess."
Hernandez was an effective starter for the Indians in 2007 (19-8, 3.06 ERA in 215 innings) and '10 (13-14, 3.77 ERA in 210 1/3 innings), but he struggled in each year between and after that. If he can return to form -- and Maddon believes he's looked similar this spring to that pitcher -- he would go a long way toward making up for the innings Tampa Bay lost by trading James Shields to Kansas City.
"I feel very close. I want to have the same year I had in 2007," Hernandez said. "I'm very, very happy to be with that group, that rotation. I'll continue to work hard and throw strikes. Keep the ball on the ground. Try not to overthrow."
Niemann has made only five regular-season appearances as a reliever, none since 2010. He has been a reliable part of the Rays' rotation when healthy -- but that's been the issue for him lately, as he's made only 31 starts over the past two years. As well as he pitched this spring, the unusually low radar gun readings didn't help his case.
"I'm here to go beat the hitters, so however I'm doing that, it doesn't matter to me," Niemann said. "If we're rocking and rolling then we know we can go do that, so whatever role or shape that is, it doesn't matter. I'm here to go out there and win."
Maddon wouldn't rule out the idea of Niemann starting a game at some point this season, but he said the team hasn't discussed the idea of putting Hernandez on a short leash. The Rays had previously been averse to putting Niemann in the bullpen because it takes a while for him to warm up, but Maddon said they would try to find ways around that until Niemann gets used to his new role.
Niemann probably won't appear in the middle of innings early in the season, for instance, and Maddon said he will have to take a wait-and-see approach regarding how long it takes him to recover after each outing.
For his part, Niemann said he will continue to build up his velocity and learn to adapt to his new job, just like former Rays starter Wade Davis did in the bullpen in 2012. This time last year, of course, Niemann beat Davis in the competition for the last spot in the Rays' rotation.
"It's another one of those really difficult decisions that we've had to make more recently," Maddon said, "because we've gotten better and we have really quality people to choose from."