Maclin tore the anterior cruciate ligament in his right knee during Saturday's practice, the same injury the wide receiver suffered at Missouri four years before the Philadelphia Eagles drafted him in the first round in 2010.
Eagles general manager Howie Roseman praised Maclin's character and decision not to hold out for a new contract.
"Jeremy's a heck of a player, great character, hard worker, he had a great offseason, and it's disappointing for him and it's disappointing for us," Roseman told The Associated Press. "He's 25 years old. He'll come back from this. He's overcome a lot of adversity in his life, he's got tremendous character. We're hurting for him, but at the same time, we have to keep going and find guys."
Maclin led the Eagles with 69 catches for 857 yards and seven touchdowns last season. He has averaged 64 catches, 863 yards and six touchdowns in his first four NFL seasons. His best season was in 2011, when he had 70 receptions for 964 yards and 10 scores.
Maclin said he'll have surgery next Tuesday. Dr. James Andrews will perform the operation in Alabama. Maclin plans to rehab in Philadelphia and be around the team.
The Associated Press contributed to this report.