Whitlock (hip) allowed one earned run on one hit and one walk while striking out eight and walking one across six innings during a rehab outing with Double-A Portland on Thursday.
Whitlock is still recovering from surgery on his hip that he underwent last September, but he is expected to make his season debut Tuesday in Tampa Bay. He's been sharp in two rehab appearances, completing 10 innings while allowing only two earned runs and punching out 14 between Boston's two highest minor-league affiliates. It's unclear if he'll be on a pitch count in his initial starts with the Red Sox, but his ability to pitch deep into Thursday's outing is an encouraging sign.