The wide receiver, chosen with the second overall pick in the draft, is the team's only rookie without a contract.
The All-America selection was regarded by some as the best player in the draft after catching 78 passes for 1,202 yards and 15 touchdowns during his junior season at Georgia Tech. He won the Biletnikoff Award, given to the nation's top collegiate receiver.
Marinelli didn't seem concerned by Johnson's absence.
"If that's a guy that has to be out, he should recover very quickly when he gets back," he said. "He did a great job in our offseason activities."