"He's progressing fine," Wren said. "I don't think he's behind or ahead [of schedule]. I just think it is progressing as you would expect. As you get closer and get the shoulder strengthened, the improvement can happen very quickly."
McCann has taken batting practice over the past couple of weeks without any problem. But he is still in the early stages of the throwing portion of his rehab program. He has completed sets of long-toss exercises at 120 feet and was cleared on Saturday to throw the ball back to the pitcher during a bullpen session.
"It's just a matter of how quickly the shoulder strengthens, responds and gets resilient," Wren said. "It's not just one day being strong. It's bouncing back the next day and being resilient and able to take the grind."
If McCann continues to make progress, he could begin participating in simulated game situations during the middle of this upcoming week. To prevent potentially damaging contact, he will not handle the catching duties or run any further than first base while participating in these games on the Minor League side over the next couple of weeks.
McCann will accompany the Braves when they return to Atlanta on Thursday and then return to the club's Spring Training complex the next week to continue working amid these simulated settings. He will build strength in his legs by catching bullpens and eventually gain clearance to begin making aggressive throws to the bases.
"As we ramp him up, it's going to be based on how it's responding and how it's coming back," Wren said. "There is no way to know. Every guy is different."
McCann will not be cleared to begin handling catching duties in games before April 16. He will be evaluated on a daily basis to determine how many Minor League games he will need to play before being cleared to return to Atlanta's lineup.
"If he's getting a lot of at-bats and the last thing is getting behind the plate to catch, that is not going to take that long," Wren said. " These are not things you plan too far in advance, because you have to allow the rehab schedule to dictate how he feels."
McCann is preparing for what will likely be the most important season of his career. While it seems highly doubtful that he returns to the Braves, the 29-year-old veteran will enter the free-agent market at the end of the year with a chance to gain a nice payday from an American League team that could utilize him as a catcher and designated hitter.
Mark Bowman is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.