The Red Sox plan to have Contreras (shoulder) split his playing time between first base and designated hitter, Jen McCaffrey of The Athletic reports.
Triston Casas' recovery from a ruptured patellar tendon is coming along well and there's a chance he's ready for Opening Day, but the acquisition of Contreras allows the Red Sox to slow-play Casas, if needed. Contreras is coming back from a shoulder injury of his own but is expected to be fine for spring training. When both players are healthy, they should soak up most of the reps between first base and DH, though Casas does have minor-league options remaining.