"I'm building my endurance up," said Drew, who added that he felt better Saturday than Friday. "It's probably what I expected -- some soreness. I think I'll deal with that for the rest of the year. The strength gains help ... now I got to try to battle out of some bad habits."
Saturday's game marked the 23rd missed game for Drew. Manager Terry Francona said they'd check on the outfielder again Monday. As usual, the Red Sox will not take batting practice prior to Sunday's day game and the same goes for Tuesday's doubleheader and Wednesday's day game, so Drew will keep working in the cage.
Francona said Drew took 35 reps Friday and will continue to slowly increase that amount.
"I'm not going to overdo it to jeopardize taking steps back," Drew said. "For the most part, it's just building up endurance. Once we get to that point, we'll take the next step."
The 35-year-old veteran said that the injury stems simply from the "wear and tear of baseball" and inflammation in the rotator cuff. He had AC joint surgery a few years ago that also causes some immobility in the shoulder.
He added that surgery after the season is a possibility.
Drew is hitting .219 this season with four homers and 21 RBIs.