The right-hander said Wednesday that he is scheduled for a second MRI on his injured right wrist.
"It's basically getting another opinion because the first one showed two different things," said Tomlin. "We're still not sure what it is, how it happened, and when it will clear up."
The Indians are not certain when Jack Hannahan will return, either, after the third baseman missed his third straight game with lower back soreness. He also is scheduled for an MRI.
"He said he is feeling better, but he's not playable," manager Manny Acta said. "We have to wait and see how his next reading goes."
Acta threw batting practice to Grady Sizemore, who had lower back surgery March 1. The manager was encouraged by what he saw from the former All-Star outfielder, but cautioned that Sizemore is not close to playing form.
"We're not going to rush anything," Acta said. "He's going to get plenty of at-bats on a rehab assignment -- but he's not even close to doing that."
Tomlin doesn't think he will be sidelined for a prolonged period. He is wearing a protective sleeve over a splint along his right wrist and forearm.
"It's very frustrating, though, because I'm not sure what I did," he said. "It just kind of came up."
Tomlin has not pitched since going 7 1/3 innings in a no-decision against the Chicago White Sox on May 7 in the rain. He experienced inflammation in the back of his wrist a couple of days later and said it may have stemmed from gripping the ball a little harder after a couple rain-slicked pitches slipped out of his hand.
"That's the only thing I can think of, but the trainers are not sure that's right either," Tomlin said.
Tomlin said he doesn't think surgery will be required and that team trainers want to take a look at the second MRI before deciding a course of action for rehab.