"There's no timetable," O'Day said. "When I talk to these medical professionals, nobody will put a timetable on it because they're good at their jobs, so they know that everybody has different experiences with this. So I'm antsy to get back, get going, but it's just a matter of doing it once and doing it right instead of reinjuring it."
Though he was officially placed on the DL in early June, O'Day said he first injured his hamstring against Houston on May 24. He still pitched a scoreless frame in Baltimore's 3-2 loss and reappeared twice at Cleveland and once more against Boston.
This time around, O'Day doesn't want to rush his recovery while keeping his eagerness at bay.
"Part of my delivery is bending over, stretching the hamstring. Before I get on the mound, I want to make sure it's fully healed, so it won't happen again," O'Day said.
The righty is 2-1 with a 3.15 ERA in 22 appearances this season.
Orioles manager Buck Showalter understands that with an injury like a hamstring, the recovery time is both slow and unique to each individual.
"He gets frustrated," Showalter said. "About 10 seconds after seeing Darren, I can tell what kind of day he's having. [Wednesday] wasn't real good and today he made some progress. When you have that hamstring in the upper end of it, that's one that is slow. Obviously he's not going to make the day after tomorrow, which is his eligibility day, but if you push too hard, you can have a setback.
"I'm trying to make him understand, just because he doesn't get better in 24 hours doesn't mean he's had a setback. He'll do it maturely, but he wants to be back tomorrow. Once he gets going, it'll be an outing or two before he gets back."
• After appealing, a date for the hearing of Manny Machado's involvement in Baltimore's benches-clearing altercation with Kansas City on June 7 has not been set. Machado charged the mound after being hit by a pitch from Royals right-hander Yordano Ventura.
"If we have a hearing, it would be on that date, so depends on whether you have a hearing or not," Showalter said. "A decision's got to be made. That's kind of Manny's decision, not ours, about whether he wants to have a hearing or not. Did Ventura have one? Is he going to have one? A lot depends -- you obviously have an idea at four days what it is -- and if you're OK with that, you can forego the hearing, right? But if you think it's not just, then you have a hearing sometime next week. It won't be this week. So far. That may change [Friday]."
• Odrisamer Despaigne, the reliever filling in for Vance Worley, who was placed on the 15-day DL with a groin strain, made his debut for the Orioles, pitching 2 2/3 innings on Wednesday against the Red Sox after being recalled from Triple-A. He gave up three hits and two walks in the 6-4 loss.
"He's going to throw the kitchen sink at you," Showalter said of Despaigne's role. "He threw about five pitches warming up and told [bullpen coach Dom Chiti], 'Dom, I'm ready. Tell him I'm ready.' He's done this before. He's been down a lot of roads, he's experienced. I think his contribution is going to be, hopefully, getting people out."
• Shortstop J.J. Hardy, sidelined since May 1 with a foot fracture, is expected to return this weekend.
"I'll talk to him on the way to the airport and he'll give me a yes or no," Showalter said. "It's pretty simple. It's not very complicated. If not yet, he'll go again [Friday], I think, in Frederick."
Deesha Thosar is a reporter for MLB.com based in Boston.