"[Jason] Berken, [David] Hernandez and Tillman are all vying for the fifth slot," Trembley said. "That's why we've tried to stretch those guys out. "
Berken and Hernandez have both pitched predominantly out of the bullpen this spring, making their first Grapefruit League starts on Tuesday and Wednesday, respectively. Tillman has started twice and last pitched in relief following Brad Bergesen on Monday. The 21-year-old Tillman has the lowest ERA of the group -- posting a 3.86 mark in three spring appearances -- but won't just be handed the final rotation spot.
The Orioles' front four arms figure to be Kevin Millwood, Jeremy Guthrie, Bergesen and Brian Matusz. But the decision on the team's fifth starter likely won't come until the final week of camp.
"I said in the offseason before I came to camp, that's the right thing to do, that was the fair thing to do," Trembley said. "Berken and Hernandez started for us all last year. When they were here last year, I thought it was unfair to just say it's Tillman's. That's no disrespect to Tillman. That's not slighting him or trying to say anything good or bad about Berken or Hernandez."
"There's still games to be played here and we have it slotted so those guys are going to get opportunities to start here. And we will see what's best for them, but more importantly, what's best for our team."
If Hernandez or Berken don't win the final spot, Trembley didn't rule out either right-hander making the Opening Day roster as part of the bullpen. He did rule out that option for Tillman.
"I don't think that's right for Tillman," Trembley said. "He's 21 years old. I think it's way too early to start looking at him as a bullpen guy. I think he's he a starter. He should be a starter."
In his first taste of the Major Leagues last year, Tillman went 2-5 with a 5.40 ERA in 12 starts. The most heralded of the trio, Tillman has mentioned frequently this spring that he's no longer the "deer in the headlights" he was at this point last year, and has been working on incorporating a cutter into his repertoire.
The 24-year-old Hernandez made 19 starts for Baltimore last year following his big league callup on May 28. He went 4-10 with a 5.42 ERA, and has shown up this spring with a much improved delivery.
"I think last year you saw quite a difference [in his delivery] from when he threw fastballs [to] when he threw a breaking pitch," Trembley said. "He's improved his arm speed. He looks more comfortable."
In his first start in Fort Myers on Tuesday, Hernandez went 3 2/3 scoreless innings, allowing five hits and a walk and picking up a pair of strikeouts.
"I'm just going to go out there and try to put up zeros, and it doesn't matter if I'm starting or a reliever," Hernandez said. "I'd definitely like to be a starter, but if they need me in the bullpen, then so be it. I'll be more than happy and I'll be ready."
Added Berken: "I look at it as regardless of what my role is or what my spot is or what I am competing for, I have to go out there and pitch well."
"I don't look at it as, 'I have to beat so and so,' or whatever," Berken said. "I don't put any extra thought into it. Chris, Dave and I are all good friends. We are all pulling for each other."
Berken went 6-12 with a 6.54 ERA in 24 starts last season and pitched a solid first six outs in Wednesday's game before an error led to a three-run third inning.
With a small spring sample size, Trembley said he will take into account the trio's performances last year and in this year's camp.
"Maybe not equally as much," Trembley said. "But you still filter in and gather as much information as you possibly can. "
"You wait [and] be patient. Give them all opportunities to pitch, see how it all falls. They'll let us know; they'll make the decision."
Brittany Ghiroli is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.