The club also re-assigned outfielder Trevor Crowe and catcher Wyatt Toregas to the Minor League camp.
Miller pitched 14 scoreless innings this spring, including five shutout innings in his final Grapefruit League start Monday against Atlanta. But the Indians want the right-hander to continue to start every fifth day in the Minors, so keeping him around as a reliever was not an option.
"Can't ask him to do much more than he did," manager Eric Wedge said. "Impressive as his stuff was, the way he handled himself was impressive right along with his stuff."
Sipp, a non-roster invitee, was 1-0 with a 3.00 ERA in six games. The 23-year-old left-hander struck out seven and walked two in six innings of work.
"I think he got better as the camp went along," Wedge said. "We used him later in ballgames, he thrives later in ballgames. He's a guy that's going to help us at some point in time this year. [He's got a] good fastball, good deception, lot of toughness and a lot of presence there for a young pitcher."
The switch-hitting Crowe, another non-roster invitee, batted .259 with a double and two RBIs in 27 at-bats. The Indians want the 23-year-old to continue to work on his play at both corner outfield spots. He will probably start the season at Double-A Akron.
"[He was] very impressive," Wedge said. "Everywhere we had him this spring, he did a really good job. Like any young player, he still has some things he needs to work on, and some areas that he needs to still finish off, but obviously we're very pleased with what we saw this spring.
"He's going to play both corners [to] get him comfortable at both corners, and we'll still keep him alive in center field too, in terms of his work."
Toregas, who will probably start the season at Akron, batted .077 (1-for-13) in nine games. Wedge was impressed with other areas of the catcher's game.
"I'd heard so much about him, just in terms of his ability to catch and obviously his ability to throw, [and] he's as good as I've seen," Wedge said. "I like the way he works a game behind the plate, the way he thinks behind the plate.
"He's the type of guy who has a chance to [have] an impact on the pitching staff [and an] impact on the ballclub. He has to continue to work and learn how to hit, but he has some time to do that."
Slocum had appeared in only three games because of a hamstring problem.
"The hamstring kind of put him behind a little bit, but I think he's come on strong here, so it's time for him to get built up," Wedge said. "We need to give him time to catch up."
The moves left the Indians with 39 players in the Major League camp. Rosters must be reduced to 25 by Opening Day.
Strength in numbers: Some managers would prefer one regular at a position rather than a platoon, but Wedge believes the Indians' situation with talented starters sharing a position can be a strength.
"I do think that," Wedge said. "It's always dependent on the year and dependent on the ballclub and personnel, [but] versatility is always a good thing, it can help protect you [against] injuries, allow you to potentially hopefully throw out the best lineup that you can on that particular day."
The Indians will have Jason Michaels and David Dellucci splitting time in left field this season depending on the opposing pitcher, and Trot Nixon and Casey Blake sharing right-field duties. Blake will also share third-base innings with Andy Marte as well as fill in occasionally at first base.
So many interchangeable pieces of the lineup puzzle give Wedge the versatility he seeks.
"In the American League, a lot of times it's tough to keep position players fresh and maybe guys that aren't maybe starters," Wedge said. "But we're going to have more than nine starters out there because we're going to be doing some platooning and we're going to have action late in the ballgames whether we're ahead or behind, so we should be able for these guys to see some playing time."
Quotable: "That's a possibility. If that's going to be the best scenario for us, the way our bullpen sets up, it's always nice to have two. I don't think it's necessary, I definitely don't think it's mandatory, but if your bullpen works out as such, it's always a positive, maybe a little bit less for us because we've got three left-handed starters." -- Wedge, on whether the team would go with two lefties in the bullpen
Quotable II: "Did you see where that hit, right behind my head? Somebody throws a punch, you duck. I ducked." -- Wedge, on a foul ball off the bat of Tampa Bay's Akinori Iwamura during Tuesday's game that narrowly missed the Indians manager
Extra bases: Because of the off-day Wednesday, Jeremy Sowers will pitch in a Minor League game in Winter Haven to stay on his regular schedule. ... The Indians are having most of their center-field prospects learn the corner outfield spots as star center fielder Grady Sizemore is only 24 years old. "You see us doing it with [Shin-Soo] Choo, doing it with [Franklin] Gutierrez, [Ben] Francisco," Wedge said. "You can't predict how it's going to play out between left field and right field, so you need to make sure they're getting reps on both sides." ... Marte made a nice barehanded grab and throw to throw out Tampa Bay's Jorge Cantu in the fourth inning. Marte also had the Indians' only hit in the 7-0 loss to Tampa Bay. "Couple nice plays by Marte, couple of nice plays by [first baseman Ryan] Garko," Wedge said. "Good to see that now." ... The Devil Rays raked Indians starter Jake Westbrook for 11 hits and seven earned runs in four innings. "It's just one of those things," Wedge said. "Jake's been outstanding all camp, we didn't play very well behind him. You expect to see that every now and then." ... Wedge was also going to give the offense a mulligan on the day. "I've been happy with the progress," Wedge explained. "It's more of an individual thing right now, I thought Grady [Sizemore] had a couple of better swings today, Andy [Marte] was on the ball better, he's moving in the right direction. Garko hit the ball well, he's been doing that." ... Reliever Jason Davis pitched for the first time since March 8, allowing one hit and two walks in a scoreless sixth inning. "He hadn't been out there a while, so we weren't sure what to expect," Wedge said. ... The most impressive performance by anyone in a Cleveland uniform was the one by non-roster invitee Brian Sikorski. The right-hander pitched a perfect fifth, striking out Delmon Young and Josh Paul and retiring Iwamura on a popup. "He's had a good fastball all spring, his slider's better, he's using his splitter better, he's a guy right there on the cusp," Wedge said.
On deck: The Indians are off Wednesday and will resume play on Thursday night against the Detroit Tigers at Joker Marchant Stadium in Lakeland. Right-hander Fausto Carmona, who was named to the Cleveland rotation on Tuesday, will get the start against Detroit's Jeremy Bonderman. Game time is 6:05 p.m. ET.
Jim Molony is a writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.