SF Giants demote Houser to bullpen as Mahle nears return to rotation

With Tyler Mahle nearing a return from the injured list, the Giants are moving right-hander Adrian Houser to the bullpen and keeping rookie right-hander Trevor McDonald in the rotation, manager Tony Vitello told reporters in Miami on Saturday.

Houser, 33, signed a two-year, $22 million deal with San Francisco in the offseason (with a club option for 2028) following a career year in 2025, but the right-hander has been one of baseball’s worst starters.

Over 14 starts, Houser has a 2-6 record with a 5.73 ERA and 5.33 FIP over 66 innings. Per Baseball Reference, Houser has been worth -0.9 WAR, the lowest of any Giant pitcher this season.

Houser has plenty of experience as a reliever, having made 48 appearances out of the bullpen in his major league career. As a multi-inning reliever, Houser has a 2.32 ERA and 3.96 FIP over 97 innings.

The Giants never used an opener for Houser, which could’ve been a viable option given Houser’s success against right-handed hitters (.218 batting average, .347 slugging percentage) and struggles against left-handed hitters (.339 batting average, .619 slugging percentage).

Mahle, placed on the injured list in late May with a left hamstring strain, will make his return to the mound on Wednesday against the Athletics, but the 31-year-old righty will need to prove he’s worthy of staying in the rotation. Before hitting the injured list, Mahle posted a 6.04 ERA and 4.88 FIP over his first 11 starts.

Rookie left-hander Carson Whisenhunt impressed in his season debut on Thursday, allowing two runs over five-plus innings against the Atlanta Braves’ formidable offense. Whisenhunt, the 27th man for Thursday’s doubleheader, has since returned to Triple-A Sacramento, but the 25-year-old is clearly the next starter up.

McDonald, 25, has had some ups and downs since joining the rotation in mid-May but has impressed on the whole.

Over eight starts, McDonald has a 4.64 ERA and 3.87 FIP over 42 2/3 innings with 41 strikeouts. McDonald is posting a groundball rate of 57.7 percent, which ranks in the 96th percentile of all qualified pitchers.

Oliva designated for assignment

Outfielder Jared Oliva was reinstated from the 60-day injured list (left wrist hamate fracture), then designated for assignment on Saturday.

Oliva, 30, made the Giants’ Opening Day roster despite being a non-roster invitee in spring training, his first time being in the majors since July 2021. The outfielder seldom played, going 1-for-7 with a run scored and a steal before sustaining an injury in mid-April.

With rookie Jonah Cox already on the roster, Oliva’s role as a speed-and-defense-first outfielder would’ve been redundant on this team.

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This story was originally published June 20, 2026 at 1:04 PM.