Aro and Rollins are in uniform, and available for Friday night's series opener against the Red Sox at Fenway Park.
Miley was scheduled to start Saturday's game against his former Red Sox team, and the Mariners haven't announced who'll take his place yet, but rookie right-hander Adrian Sampson has joined the team from Triple-A Tacoma, and appears the logical choice to be activated on Saturday.
Miley said his shoulder was nagging him his last couple of starts, but he doesn't think it's a serious issue. He expects to come off the DL as soon as he's eligible on June 28.
"About two, three weeks ago, I thought it was normal shoulder soreness, but it kept barking, and getting worse and worse rather than going away," Miley said. "So I'll go ahead and take a couple days off, and get it right."
Hernandez also isn't expected back for several more weeks as he nurses a strained right calf that has sidelined him since late May. Hernandez has started playing catch from a standing position, but is still unable to push off on his right leg.
"We are trying to patch things together," said Mariners manager Scott Servais, who indicated Hernandez is reporting some progress, and is feeling better as he continues rehabbing in Seattle.
Servais is optimistic that Miley's own rehab will be brief.
"He's been struggling a little after his last start," Servais said. "His shoulder was bugging him a little bit. I don't think it's anything more than getting it calmed down. We thought it best to shut him down, and give him a chance to regroup. We're optimistic it will only be a couple starts."
Miley didn't want to be placed on the DL, believing he could pitch through the problem, particularly with the Red Sox next up on his schedule.
"You always get a little extra adrenaline when you come back somewhere you've been before," he said. "It would have been my first time doing that, I was looking forward to it. I'd just got done talking with [Red Sox right-hander Rick] Porcello. We were going to match up, but it's one of those things where we're just trying to be smart."
Miley said there was talk of pushing his start back to Sunday or Monday, but "we need a little help right now, so they went ahead and did the DL."
That decision will likely open the door for Sampson to make his Major League debut. The 24-year-old was acquired from the Pirates last July 31 in a trade for veteran J.A. Happ. The native of Redmond, Wash., is 7-4 with a 3.25 ERA in 13 starts for Tacoma. Sampson pitched for Skyline High School and Bellevue Community College before being drafted by the Pirates in the fifth round in 2012.