Before the injury, Beckett had been far from the dominant ace of seasons past. He's sitting on a 4.14 ERA and 101 ERA+, meaning he's been precisely league-average. He has been better of late; after getting shelled for seven runs in two innings against Cleveland on May 10, he had a 5.97 ERA. Still, his mediocrity has helped the Red Sox languish near the cellar of the AL East well into June.
Morales has a 3.04 ERA in 23.2 innings pitched this season with 20 strikeouts. He likely won't pitch deep into the game Sunday, but if Beckett has an extended stay on the shelf, he'll be able to work his way deeper as he gets more comfortable starting again.