DETROIT -- There remains no definitive timetable for Andrew Miller's return to the Indians' bullpen, but the big left-hander took another promising step forward on Friday afternoon. Prior to the Tribe's game against the Tigers, Miller worked through a lengthy bullpen session at Comerica Park.
"The fact that he threw 30 pitches -- that's a lot," Indians manager Terry Francona said. "Where it goes from here, I don't think we know. Obviously, he's going to have to throw more. One, we just want to see how he bounces back, first of all, because that's one of the huge challenges."
Due to the volume of throws in Friday's workout, Francona was not sure if Miller would log another bullpen session during the current weekend series in Detroit. The next workout will likely come during the team's next road series in Chicago, where the Tribe begins a four-game set against the White Sox on Monday.
Francona was non-committal when asked if Miller -- working through mechanical issues stemming from right knee discomfort -- would require a Minor League rehab assignment before coming off the 10-day disabled list.
"Like we did last time, we'll get together as a group when it's [the appropriate time]," Francona said. "And he'll be a part of that, because I mean, shoot man, he knows his body better than we do. You guys are around him. He's about as conscientious as they come, so he will be a part of that decision."
Plutko to start Tuesday
With a need for a fifth starter looming on Tuesday against the White Sox, the Indians have discussed going with either Adam Plutko or Shane Bieber from Triple-A Columbus. Cleveland plans on promoting Plutko, and the decision comes after some hefty internal dialogue.
Chris Antonetti, the Indians' president of baseball operations, sought the opinions of Columbus pitching coach Steve Karsay, Minor League pitching coordinator Ruben Niebla and Tim Belcher, a special assistant to baseball operations, among others, in determining whether to go with Plutko or Bieber for the fifth spot.

"I don't think it's bad to have a split camp when you've got two guys you think are pretty good," Francona said. "And they really did a good job of laying it out, how they felt. And, I think that after reading that, it seemed like Plutko was the right choice for various reasons. And I understand it, and I really kind of respected the way that they went about it."
Plutko has gone 3-0 with a 3.93 ERA in three starts this season for Cleveland, but has spent the bulk of the year at Triple-A. In nine Minor League outings, the righty has a 1.83 ERA with 48 strikeouts against 10 walks in 59 innings. On Thursday, Plutko allowed one run and struck out five with no walks in six innings against Norfolk.
Worth noting
• Francona noted that outfielder Brandon Guyer (10-day DL, neck strain) will continue on his Minor League rehab assignment at least through this weekend. The Indians are not facing a left-handed pitcher (Guyer's specialty) in Detroit, and the outfielder has gone 2-for-40 between Triple-A and Double-A in 10 rehab games this year.
"He knows he needs the at-bats," Francona said. "Hopefully, it can help him, because shoot, when we get him back, I don't know how many times I've said it, we've got to have him do some damage when he's facing lefties."
• Outfielder Tyler Naquin (10-day DL, left hamstring) was scheduled to play five innings with Triple-A Columbus on Friday, per Francona. The Indians' manager noted that Naquin will move between right and center field over the next week, while building up to playing nine innings.
• Left-hander Jeff Beliveau, who was designated for assignment on Saturday, cleared waivers and has accepted an outright assignment to Triple-A Columbus.