"While Dustin Pedroia got the green light to return to the Red Sox after his nearly two-month absence, recent acquisition Carlos Delgado suffered a potential setback in his attempt to return to the major leagues for the first time since May 2009.

Delgado said that his lower left back has felt sore for the last few days, and that it stiffened on him after he struck out in the second inning of Triple-A Pawtucket's 3-1 win against Buffalo yesterday. He was replaced by Lars Anderson in the fourth.

"My left side on the lower back area was a little stiff, so it was kind of like bothering me enough (that) I just came out of there and got a little treatment," said the first baseman, who is 3-for-13 with two RBI in five games with the PawSox.

"It bothered me a little bit on the swing. It's been a little sore the last couple of days, and we didn't really think too much of it. It got to the point where it got pretty tight, and I couldn't move around as well as I wanted to."

Pawtucket manager Torey Lovullo said Delgado is day-to-day.

"We're going to err on the side of caution; we're not going to put him in harm's way whatsoever," Lovullo said. "He was honest with us. He said that he had a little hiccup in his back area, and we got him out of here. There's nothing more than that. He's just going to be day-to-day.""