SAN FRANCISCO -- The Giants were among the most rookie-powered teams in the Majors in 2024, so it felt fitting that they had one more debut on tap for Game 162.

Trevor McDonald fired three hitless innings in his Major League debut on Sunday afternoon, providing a bright spot in the Giants’ 6-1 loss to the Cardinals at Oracle Park, which sealed a losing season (80-82) for San Francisco.

With the Giants in need of a fresh arm after running a bullpen game in place of Blake Snell on Saturday, McDonald unexpectedly earned his first big league callup, receiving the news just as he was about to tune in to the Georgia-Alabama football game on Saturday night.

McDonald had been on standby in Arizona since Triple-A Sacramento's season ended Sept. 22, but he was planning to fly home to Louisiana and begin his offseason on Sunday morning. He found himself canceling that flight and making a last-minute detour to San Francisco instead, walking into the Giants' clubhouse a few hours before first pitch.

“Better late than never,” said McDonald, the Giants’ No. 12 prospect per MLB Pipeline.

McDonald’s parents, Misty and Larry, and his uncle, James, also managed to catch a flight from New Orleans on Sunday morning and got to Oracle Park in time to see McDonald take the mound in the top of the seventh.

“It was awesome,” McDonald said. “I kind of stepped off the back of the mound and looked around, took it all in for a sec. Took a deep breath, tried to get composed and just do the thing.”

McDonald retired nine of the 10 batters he faced, only issuing a two-out walk to Alec Burleson in the top of the ninth. The 23-year-old right-hander punched out Pedro Pagés for his first career strikeout in the eighth and topped out at 93.9 mph with his sinker, which helped him induce seven groundouts. He became the first player to debut on the final day of the regular season since the Rangers’ Yerry Rodriguez, the Angels’ Nash Walters and the Rockies’ Noah Davis all did so in 2022.

“You know there were some nerves involved,” manager Bob Melvin said. “The first few pitches are the ones that get you a little bit. Once he got a couple of strikes, it was off to the races. He pitched really well. No hits and one walk. He’s got his sinker, and it keeps the ball on the ground. He threw really well. There were a lot of things to like about it.”

An 11th-round Draft pick in 2019, McDonald was one of three pitchers who were added to the 40-man roster over the 2023-24 offseason after recording a 1.33 ERA over 14 appearances (13 starts) across three Minor League levels in 2023. The Giants brought him to big league camp this spring, but he ended up pulling his groin on his final pitch of Spring Training, which forced him to open the season on the injured list. He finally got back on the mound in May and posted a 4.40 ERA over 23 appearances (20 starts) between the Rookie-level Arizona Complex League, High-A Eugene, Double-A Richmond and Sacramento in 2024.

“Just kind of went on the world tour this year,” McDonald said. “It’s been a lot of fun.”

With his first big league appearance under his belt, McDonald could be poised to take another step forward in 2025 and join a promising group of homegrown starters that includes Kyle Harrison, Landen Roupp, No. 8 prospect Mason Black and Hayden Birdsong, who struck out 11 over 4 1/3 innings in his final start of the year. Birdsong allowed three runs on four hits -- including a third-inning solo shot by Brendan Donovan -- and three walks, but he showcased a nasty slider, which generated 12 of his 18 swing-and-misses.

“I’m just happy I could punch guys out,” said Birdsong, who ended his rookie year with a 4.75 ERA over 16 starts. “It was fun to do that again. I know what I need to work on. I need to work on controlling the strike zone. I’ll be ready to go next year.”

Birdsong certainly won’t be the only member of the Giants who will be motivated to improve following the club’s disappointing season.

"I know this season didn't end the way we wanted it to, but we're going to go home this offseason and we’re going to get better,” third baseman Matt Chapman said in a postgame speech to the 32,348 fans in attendance. “You guys bring the same energy next year. When we end the season next year, we're going to be going to the playoffs. We're not done."