ORLANDO, Fla. -- While Indians center fielder Grady Sizemore and catcher Carlos Santana are both on schedule to be in the Tribe lineup on Opening Day, there are milestones in their respective recoveries from knee surgery that must be met this winter and there will be questions about their physical form throughout the 2011 season.Both Sizemore and Santana are currently rehabbing at the Indians' complex in Goodyear, Ariz., and said to be progressing well. Sizemore is five and a half months removed from microfracture surgery on his left knee, while Santana is three and a half months removed from surgery to repair the lateral collateral ligament in his left knee. At the General Managers Meetings, which wrapped up Thursday at the Waldorf Astoria, Tribe GM Chris Antonetti said Santana's recovery is a bit more predictable, simply because more players have undergone repaired ligaments than microfracture procedures. "With Grady, it's a little less certain," Antonetti said. "We'll have to continue to see how he meets the individual milestones and be in touch with Dr. [Richard] Steadman [who performed the surgery] on what he feels the appropriate progression will continue to be. He's met all his checkpoints so far." Sizemore -- a three-time All-Star, two-time Gold Glove Award winner and one-time Silver Slugger Award winner who has been limited by injury to just 139 games played over the last two seasons -- has progressed from water-based to land-based exercises. He's currently doing squats and riding the stationary bicycle. He's expected to progress to running on the treadmill by early January and is expected to begin hitting and throwing at that time, too. If Sizemore has a setback, though, his availability for Opening Day could begin to come into question. "There's no reason to be concerned, as far as his availability for us," Antonetti said. "But it's a delicate balance. Between the beginning of January or the middle of January, that's only two weeks, but it has significant implications on when he'll be ready for the season. We'll have a much better sense in January [of his timeline] than we do now." Santana, meanwhile, has progressed to full lower body strength and conditioning. He's scheduled to initiate a land-based, walk-jog progression later this week. He, too, is scheduled for baseball activities beginning in early January. The Indians expect to begin working Santana -- who was stellar in his first 46 big league games before wrenching his knee in a horrific home-plate collision in early August -- in at first base next season to prevent some of the wear and tear on his body that the catching spot provides. A comparable to note in consideration of Sizemore's and Santana's circumstances is the case of Matt LaPorta this past season. LaPorta spent all winter recovering from hip and turf toe surgeries in an effort to be game-ready for Opening Day. But there is a difference between merely being game-ready and being in peak baseball conditioning, and that's a battle Sizemore and Santana will likely wage in 2011. LaPorta said at season's end that he never felt his legs fully under him until the tail end of the year. At this point, the Indians are pleased with the progress of both Sizemore and Santana, who figure to feature prominently in the lineup next season. But all expectations for their performance in 2011 must be measured, because while time heals all wounds, the healing doesn't always mesh with baseball's calendar.