After a marathon session of testing yesterday at the University of Pittsburgh Medical Center, Stephen Drew has been cleared to resume baseball activities. But that still doesn't mean the veteran shortstop will be ready for Opening Day. "We'll probably have a better sense of that by the end of the weekend, but we're starting to fight the calendar a little bit," GM Ben Cherington said here today. "We don't want him to be in a position where he's having to rush to get at-bats to make it by a certain date." As a result, manager John Farrell said the Red Sox likely will have Drew take at-bats in minor league games in order to assure they will be able to backdate a possible stint on the 7-day disabled list (players who suffer a concussion can be placed on the DL for shorter than the usual 15-day term). According to both Farrell and Cherington, Drew already passed the Major League Baseball-mandated concussion tests several days before he traveled to Pittsburgh on Wednesday to see specialist Dr. Mickey Collins. The trip to see Collins was more for Drew's peace of mind about why he wasn't entirely symptom-free. He still was experiencing some blurry vision.