Baker, 30, last started in a Minor League game on Thursday, throwing 23 pitches in two scoreless innings. He previously pitched in a "B" game against the Pirates on March 10, and began to feel discomfort in his elbow shortly thereafter.
Baker was plagued by injuries last season, when he was placed on the disabled list twice in the second half of the season with elbow problems.
Baker posted a career-low 3.14 ERA last season, but in only 134 2/3 innings, as he threw just 24 innings after the All-Star break due to injury.
So although Baker wants to make his scheduled start in the club's home opener against the Angels on April 9, he also wants to make sure he's healthy entering the season.
"I'd love to make that start, honestly, and that's what we're shooting for," Baker said. "But obviously, we're running out of time. So I guess we'll have to see how this next start goes. Not necessarily if the results are better, but if it's coming out of my hand better. As long as I physically feel good, that's what we're shooting for."
Baker is slated to make his next start on Saturday against the Pirates, and is expected to ramp up his pitch count by about 15-20 pitches.
Baker said he's confident that he's getting closer to where he needs to be, although his velocity isn't quite at the same level it was during last season. But Baker has continually downplayed the importance of his velocity, because he says it takes him a while to build it up leading into the season.
"I know it's going to come, it's just a matter of when," said Baker, whose fastball registered at 86-89 mph against the Rays. "I know we've talked a little bit about the velocity not being there, just like I said, it all relates -- the velocity, the location, the not trying to overdo it. You have a tendency when you try to force pitches, the results are not to your liking. But sometimes it's not going to come out as good as it can."
Baker was pleased by the way his arm responded to throwing breaking balls, as the Rays did most of their damage by feasting on his fastball. Ben Zobrist hit a two-out grand slam on a first-pitch fastball in the second inning, while Eliot Johnson hit a two-run homer off a fastball with two outs in the third.
"I think there were a couple of really good changeups," Baker said. "But that's part of it. The pitch selection wasn't quite there. I was more concerned with throwing some fastballs down. I threw some decent breaking ball, some decent changeups. Maybe not as many as I needed to, to slow them down. But that's OK. It's a change I can make regarding pitch selection."
Baker is trying his best to stay on track for the home opener, but he also knows that there's a chance he could be moved to the back of the rotation to get his first start on April 15 because of an off-day on April 10.
"We're going to make a wise decision either way," Baker said. "We've got a long season. To sit here and say that's the most important thing -- to make that home opener start -- that's just not the case. Obviously I'd love to make that start, but if I can't, I can't."