Receiver Stevie Johnson missed the Buffalo Bills' first two voluntary minicamp practices because of a sore back.
Calling the injury a "mild strain" Wednesday, Johnson says he felt a tweak while warming up before the team's first practice a day earlier.
He'll be re-evaluated to determine whether he can practice in the final minicamp session Thursday.
Johnson was disappointed not being able to work with newly signed quarterback Kevin Kolb, who is competing for a starting job. The practices were also the first run by new coach Doug Marrone, who took over in January after Chan Gailey was fired.
Johnson has led Buffalo in yards receiving in each of the past three seasons. He missed most of the offseason minicamps last year after having groin surgery.