The reliever entered in the bottom of the 8th inning and retired the only batter he faced, Mike Napoli, on a grounder to third. He was then replaced with a left-handed batter coming up.
O'Day received injections in the right upper palm and right wrist to reduce the inflammation in a tendon that was causing a pinched nerve in his hand, an injury that had been bothering him for nearly a month and forced the Orioles to shelve him last week.
O'Day rejoined the team Wednesday, but manager Buck Showalter said after that night's game that he hadn't been available to pitch yet.
"I'm glad to be back," O'Day said Thursday afternoon. "It's the most fun time of the year. Basically you play the whole six-month season to play in the playoffs, and it's getting down to that time. I'd be pretty upset if I had to miss that. I've already missed a couple of weeks of it. I'm ready to get going. …It was definitely frustrating because we didn't know what it was. One day it would feel good and the next day I'd go out there and it would feel worse. It was tough."
O'Day, who owns a team-best 2.28 ERA, pitched just twice since Aug. 28, with rookie right-hander Kevin Gausman picking up some of his late-inning setup duties. In two scoreless innings Wednesday, Gausman struck out five batters, including four straight.
"There's a lot of talent down there," O'Day said. "I think, being in the bullpen, especially a bullpen where we play in a lot of close games, you learn a lot about pitching. I don't think Kevin is going to be in the bullpen for too long. I think he's going to be a great starter, but him spending some time down there has probably taught him a few things."
Now that O'Day has returned, Showalter indicated that Gausman — who wasn't available Thursday after pitching back-to-back nights — could still be used in tight late-inning situations.
"I'm not going to sit and let a player get [boxed] into one role or whatever," Showalter said. "Let's see how the game dictates [it]. … Each game presents a different challenge depending on how we had to use people the last two or three nights. We've got some quick turnaround games, some crazy starting times in Tampa."
On Wednesday, Gausman nearly entirely relied on his fastball-changeup combo, throwing just one slider to strike out Napoli. He struck out David Ortiz on a 99-mph fastball, then struck out the side in his next inning, getting Napoli, Mike Carp and Daniel Nava.
"To be honest, I just tried to go out there and throw strikes," Gausman said after Wednesday's game. "It's something that I've really focused on more than anything coming out of the pen. You can't walks guys, especially in a tight game like tonight. I'm still kind of getting used to throwing out of the bullpen, but I felt comfortable out there."
Hammel ready for next start
Right-hander Jason Hammel, who will make another spot start Friday night against the Tampa Bay Rays, said he's feeling as healthy as he has since the beginning of the season and is excited to be back starting.
"It's really my role," Hammel said. "I am a starter. I'm never going to leave that mindset, but it's nice that I'll get another one and I think I can build on what happened last time. I made one bad pitch in my last outing, and other than that it was pretty good. In my side work yesterday I felt even stronger. I'm very excited."
Making his first start since July 28, Hammel — who spent five weeks on the disabled list with a right forearm strain — allowed three runs over five innings Friday in Toronto. He said he hasn't been told of any pitch count or inning restrictions for Friday. He was removed last Friday after just five innings.
Hammel said that being healthy has improved his ability to throw his curveball and slider.
"I can honestly say that I feel a lot better, and it's a noticeable difference with the breaking ball," Hammel said. "If you can't throw the breaking ball for strikes or feel like you can control them, it's going to be hard to use only your fastball. Big league hitters know how to hit stuff when you're not able to get ahead on breaking stuff. You get hit around when you can't use other pitches effectively."
Rotation in flux
Gonzalez, who left his start Sunday with a right groin strain, threw a bullpen session before Thursday's game in Boston and he felt good, Showalter said. Norris, who missed his past turn in the rotation with elbow stiffness, threw a bullpen session Tuesday.
If they're healthy, Showalter might need both of them to start during the Orioles' four-game series in Tampa. Showalter indicated that a pitcher might have to leave the team because of a family illness, but he wouldn't elaborate.
"There's some ill health, it's something they might need to shoot home for," Showalter said. "It could affect us and our ability to go different directions here."
Right-hander Scott Feldman is scheduled to pitch Sunday, and lefty Wei-Yin Chen is scheduled to start Monday.
Around the horn
Asked his rationale for pinch hitting Steve Pearce, who had been on the DL since August with left wrist tendinitis before being activated Tuesday, instead of Michael Morse in the 12th inning Wednesday against Boston left-hander Franklin Morales, Showalter said Pearce offered a better matchup. Pearce had previously never faced Morales. "He's a little bit more experienced at pinch hitting, and he's had some contributions in this ballpark," Showalter said. … Designated hitter Danny Valencia entered Thursday with 10 multihit games in his past 17 games and was batting .467 (28-for-60) in that span. … Since 2010, Matt Wieters led all major league catchers with 174 extra-base hits entering Thursday's play. The St. Louis Cardinals' Yadier Molina had 173 and the Texas Rangers' A.J. Pierzynski had 155.