McDonald was a limited participant in Wednesday’s practice, but his inability to take the field Thursday puts in jeopardy his chances of playing in Sunday’s regular-season opener at the Cleveland Browns.
Entering his sixth NFL season overall and second with Pittsburgh, McDonald had 14 receptions for 188 yards and a touchdown in 10 games (seven starts) last season.
If McDonald is unable to play Sunday, veteran tight end Jesse James is expected to start in his place.
James started 14 games last season and established career highs with 43 receptions for 372 yards and three touchdowns.
A fifth-round draft pick out of Penn State in 2015, the 6-foot-7, 261-pound James had 39 catches for 338 yards in 16 games in 2016.
McDonald was a second-round pick of the San Francisco 49ers in 2013 out of Rice. He had only 10 catches in his first two seasons before hauling in 54 receptions and seven touchdowns over his final two years in the Bay Area.
McDonald was the only player who did not practice for Pittsburgh on Thursday.
The Steelers have won the past six meetings against AFC North rival Cleveland, but the last three have been decided by four points or fewer.