O'Brien said recently that he wants to put on "as much muscle as I can" this offseason in order to help his body absorb the toll of the 2027 season, Daniel Guerrero of the St. Louis Post-Dispatch reports.
O'Brien finished tied for the National League lead with 38 saves this season, but he faded after the All-Star break, posting a 5.11 ERA, 1.54 WHIP and 25:16 K:BB over 24.2 innings while blowing four of 18 save chances. The 31-year-old also saw his velocity dip in the second half, as he averaged 97 mph with his four-seamer after averaging 98.2 mph with the pitch in the first half. As things stand right now, O'Brien is the clear favorite to open next season as the Cardinals' closer again.