SEATTLE -- Cal Raleigh knew something was off immediately, pacing out to the mound after Bryan Woo unleashed what would be his final pitch on Friday night.

Woo winced after his 62nd offering, showing discomfort but not extreme pain, which he revealed postgame to be tightness in his pitching forearm. His body language didn’t suggest that something significant was afoot, but given that he’d just been activated off the 15-day injured list with right elbow inflammation and was making his 2024 debut, the development in Seattle’s series-opening 8-1 win over Oakland at T-Mobile Park was concerning nonetheless.

After a brief conferral with manager Scott Servais and head athletic trainer Kyle Torgerson -- and despite his own efforts to remain in the game -- Woo exited with one out in the fifth inning of a scoreless outing. The team later designated that the departure was due to “precautionary reasons." And Servais said he anticipates that Woo will make his next start.

“Just kind of take it day by day,” Woo said. “Going through injuries is never fun, but try to just do the best you can with it.”

Woo, 24, surrendered just one hit and one walk with three strikeouts, settling in after a 26-pitch first inning and looking on pace to clear the fifth, which Servais suggested pregame was the threshold for the righty -- and/or somewhere in the 80-pitch range.

Beyond limited traffic, Woo was also riding the run support of a five-run fourth, punctuated by a two-run homer from Dylan Moore. But that lengthy layover may have contributed to the issue.

“It was just sitting for a long time,” Woo said. “It was a long inning. You sit for that long, especially coming back from injuries, like it gets kind of cold and it's kind of hard to get it going again. So it's kind of been like a theme throughout the rehab process. If I ever have long innings or something like that, it's just kind of finding ways to get it going again.”

Woo wowed in three rehab appearances with Triple-A Tacoma, all scoreless and with 17 strikeouts in 11 1/3 innings, after being placed on the IL just three days before Opening Day. The efficiency at times prevented him from stretching out, capped with 67 pitches in his final rehab start last Saturday.

“He'll be fine,” Servais said. “This has happened before with Bryan. He's a young pitcher. He's had issues in the past, he's worked through some things, and again, a lot of these guys are learning. ... You have the long innings like that, maybe you need to change up your routine, do some different things. But he'll make his next start.”

Woo’s next turn in the rotation is Wednesday’s matinee against Kansas City, ahead of what will be Seattle’s final off-day until June 2. In between, the Mariners are set to play 17 straight games, beginning with a tough road trip to Baltimore and New York, where the teams with the two best records in the American League await.

In the greater context of Woo’s young career, injuries have prevented him from pitching a full season dating back to college -- including last year, when he spent two weeks in August on the IL with right forearm inflammation.

Asked what methods he’ll attempt to prevent such issues, Woo said: “Throughout the inning after, try to catch a breath, get some water or whatever after an out or so. Get it moving again, stretches, throwing weighted balls -- kind of obviously still trying to figure out what works for me, but yeah, just kind of trying different things.”

Aside from Woo, the Mariners had little else to worry about on Friday.

After the homer, Moore went on to log a career-high five RBIs, with a two-run single with the bases loaded in the fifth and another RBI single in the seventh. A pair of run-scoring doubles from Luke Raley and Ty France also helped the Mariners to reach their fourth-largest offensive output this year.

"Moore seems to be kind of kryptonite for us,” A’s manager Mark Kotsay said. “Every time he’s in the lineup, it seems like we have trouble getting him out."

Seattle has now won 13 of its past 14 games against Oakland dating back to the start of last year, outscoring the A’s, 76-26, in that stretch.