When the surgery was first announced Jan. 9, Dombrowski said the Tigers "fully anticipate Justin to participate in spring training and be in a position to compete at the beginning of the 2014 season."
But on Thursday, Dombrowski told MLive.com that Verlander's status to start the season is still uncertain.
"He's doing great," Dombrowski said. "I'm not concerned for him being out an extended period. If he misses any time of the season, it would only be a very short time period. I'm not ready to say that he will. But he's doing very well."
Verlander's rehab was initally expected to take six weeks. He is expected to play catch Monday for the first time.
Tigers pitchers and catchers report to spring training Feb. 13, while Opening Day is March 31. Verlander has started for the Tigers on Opening Day for six straight years, but this season that honor could go to reigning Cy Young Award winner Max Scherzer.
"We don't want him to push too hard," Dombrowski told MLive.com. "We want him to follow the doctor's schedule. He's been under the doctor's guidance. He's stayed there so far. He's been doing phenomenal. He's already moving around. They say he's at the point where he might start doing some movement drills and all beginning next week."