Baltimore Orioles outfielder Tyler O'Neill will start Monday's series opener against the hosting Arizona Diamondbacks at Chase Field on the bench. The left-handed-hitting Ryan O'Hearn will start in right field and will bat third against D-backs right-hander Zac Gallen. O'Neill homered yet again on Opening Day to get off to a nice start in his first year in Baltimore, and he's continued to hit well in his first nine games, going 11-for-33 (.333) with three doubles, a triple, seven RBI, six runs scored, three walks and eight strikeouts in 37 plate appearances. Expect O'Neill to return to the starting lineup on Tuesday in Phoenix. O'Hearn should be a popular DFS sleeper on Tuesday in the matchup against Gallen, who he has hit .375 against with two RBI in a small sample size of eight at-bats. O'Hearn is searching for his first homer of 2025 and has gone 6-for-22 with three runs scored early on.

St. Louis Cardinals catcher Ivan Herrera (knee) has been diagnosed with a bone bruise in his left knee after getting more tests in St. Louis on Monday and will miss a minimum of four weeks, according to manager Oliver Marmol. With Herrera on the injured list for the foreseeable future, Willson Contreras isn't a candidate to return behind the plate, according to Marmol. Herrera was forced to leave in the third inning in Game 1 of the team's doubleheader on Sunday against the Boston Red Sox at Fenway Park. It's a tough break for the 24-year-old native of Panama, as he was off to a red-hot start at the plate in 2025 as the Cards' primary catcher, going 8-for-21 with four home runs, two doubles, 11 RBI and six runs scored in his first seven games. Given his excellent start, he's worth stashing in deeper fantasy leagues. Pedro Pages will now be the primary backstop, with Yohel Pozo backing him up.

St. Louis Cardinals third baseman Nolan Arenado (illness) has been scratched from Monday's series opener at PNC Park against the division-rival Pittsburgh Pirates due to an illness and soreness, according to manager Oliver Marmol. Thomas Saggese will replace him at third base and will bat sixth against Pirates right-hander Carmen Mlodzinski. It doesn't sound like anything serious for Arenado, who should be considered day-to-day, and fantasy managers will want to check back on him on Tuesday. The 33-year-old veteran has looked great in the early going, batting .343 (12-for-35) with a homer, six RBI and six runs scored in 35 at-bats. Saggese, one of St. Louis' top prospects, hit his second career home run on Sunday night against the Red Sox and is 2-for-4 with four RBI in just two games in 2025. He should be considered a DFS sleeper against Mlodzinski, who he has faced only one time in his career.

Seattle Mariners second baseman Jorge Polanco (side), who missed the team's last two games due to soreness in his side, is back in the starting lineup for Monday's series opener against the visiting Houston Astros at T-Mobile Park. Polanco is the designated hitter and will bat second, with Ryan Bliss playing second base and batting eighth against Astros right-hander Hayden Wesneski. Fantasy managers will want to get the 31-year-old Polanco back in their starting lineups to begin the week with the veteran switch-hitter going 9-for-20 with two home runs and eight RBI in his first six games for Seattle in 2025. Polanco also has a homer and two RBI in only three career at-bats against Wesneski. If the Dominican infielder can get through Monday's contest without a setback to his side, he could return to second-base duties as soon as Tuesday.

Seattle Mariners right-hander George Kirby (shoulder) "felt great" during a bullpen session over the weekend, according to general manager Justin Hollander. Kirby will throw two more bullpens this week and then start a more traditional game progression. The Mariners don't have an official timeline for Kirby to make his 2025 season debut, but it sounds like May is more likely at this point. The 27-year-old started the year on the injured list after being diagnosed with inflammation in his right shoulder back in early March in spring training. It caused most fantasy managers to pass on the former first-rounder in drafts, but he's been making good progress and might only have to miss the first month of the season. Kirby is an elite control artist and will be valuable in all fantasy leagues once he's healthy, but he's also sported a below-average strikeout rate in his three big-league seasons.