"He just ran out of time," trainer Kevin Rand said before the Tigers' game against the Baltimore Orioles at Comerica Park.
Rand went on to say that Martinez, who tore the anterior cruciate ligament in his left knee while working out in January, won't even begin running until November.
"He has worked extremely hard to give himself a shot at coming back this year," Rand said. "But unfortunately the leg strength isn't there."
Martinez underwent microfracture surgery but didn't require complete ACL reconstruction. An MRI taken at the end of June showed healing was progressing to the point there was hope he might return this season.
In recent weeks, however, that hope turned to doubt.
Assistant general manager Al Avila a couple of weeks ago prepared Tigers fans for the bad news, saying: "For me, that (Martinez returning) would be a longshot. From what I understand, they want him to get 100 percent in the one leg before he starts doing everything on two."
The Tigers still expect Martinez to return next year, when he'll be their full-time designated hitter.
Martinez, 33, hit .330 with 12 homers and 103 RBI as the Tigers advanced to the American League Championship Series in 2011.