Wells has an unresolved issue affecting his equilibrium. The team had hoped he could be cleared by doctors to join the club Friday in Texas, but instead he's likely done for the year.
Ryan has been receiving treatment for a disk issue in his neck in Seattle as well.
Wells' situation had apparently been developing in recent weeks as he struggled with his vision and balance until it reached a point where he stayed home to undergo tests when the team embarked on its current seven-day road trip.
"Right now they're identifying some things that are wrong with him," general manager Jack Zduriencik said. "It's basically a balance issue. He's going to go through some more tests here by the early part of next week. The big thing is he's gone through some things that I don't think even he realized he was going through."
Wells was impressive when the Mariners first acquired him from the Tigers in the Doug Fister deal on July 30 but tailed off badly in the past three weeks.
"If they're able to rectify his issues, now he's going to be able to come back and be a little bit different player," Zduriencik said. "We've seen some really nice things out of him. You talk about power, outfield play, throwing arm. He's an aggressive, strong, physical kid and if he can settle into where he's normal, it's going to be interesting to watch that unfold."
Wedge said Ryan, out since last Saturday with his neck issue, is continuing to improve, but indicated it's "probably a long shot now" for either player to return even for the final three-game home series against the A's from Monday through Wednesday.