The San Francisco Giants placed rookie infielder Christian Koss (hamstring) on the 10-day injured list on Tuesday with a left-hamstring strain and recalled outfielder Luis Matos from Triple-A Sacramento in a corresponding move. The Giants are now dangerously thin at third base with Koss, Matt Chapman (hand) and Casey Schmitt (hand) all on the IL. The good news, though, is that Chapman could be back as early as next Monday for the final week before the All-Star break. With Koss now sidelined, veteran Wilmer Flores will start at third and bat cleanup on Tuesday against Arizona Diamondbacks right-hander Zac Gallen. Koss, 27, is in his first year in the big leagues in 2025 and was serving as infield depth in the Bay Area, hitting .265/.305/.357 with a below-average .662 OPS, two homers, 12 RBI, two steals and 12 runs in 41 games played.

San Francisco Giants infielder Christian Koss (hamstring) was forced to leave Monday's loss to the Diamondbacks with a hamstring injury that he sustained running down the first base line in his third at-bat. He remained in the game and hit a double (after video review) in the eighth inning before being replaced by pinch runner Brett Wisely. Wisely remained in the game at third base and could get more playing time depending on how long Koss is sidelined. The team will know more after further evaluation on Tuesday, but he will at least miss Tuesday's game against Arizona and could end up landing on the injured list. The Giants have lost multiple third basemen to injury, so the position is getting pretty thin.

San Francisco Giants second baseman Christian Koss turned in a big performance in his team's 10-6 win over the Arizona Diamondbacks on Tuesday. Koss went 2-for-4 with a grand slam to help power the Giants to the win over their division rivals. The rookie infielder erased an early 3-0 Diamondbacks lead with his grand slam in the second inning while also accomplishing the rare feat of making his first career homer a grand slam in the contest. Koss is now hitting .241 with one homer, six runs, and seven RBI across 54 at-bats for San Francisco this season. Big game aside, fantasy gamers will need to see a bit more out of Koss at the plate before considering him for starting lineups in the future.

The San Francisco Giants have added infield prospect Christian Koss to their Opening Day roster. The 27-year-old was a non-roster invitee to camp this spring, but had a strong spring that prompted the Giants to retain him on the roster to begin the year. The right-handed hitter went 14-for-41 (.341) with a home run, five RBI, 12 runs scored, and a stolen base in Cactus League play, along with a 5:7 BB:K. The former12th-round draft pick owns a career .274/.339/.454 slash line in the minors with about average walk and strikeout rates. Koss will be one of theGiants' bench bats who will be making his MLB debut whenever he gets into a game, but there's not a whole lot here to get excited about for fantasy, and he can be safely left on the waiver wire for now.