Allen caught a 17-yard touchdown pass from rookie quarterback Justin Herbert with 6 minutes, 26 seconds left in the first quarter of the Chargers' 30-27 overtime loss to give them a 6-0 lead. He later was seen getting stretched out on the sideline.
Chargers coach Anthony Lynn said that Allen suffered back spasms and had no immediate estimate on how long he will be out. "He tried to come back but just couldn't go," Lynn said after the game.
Allen finished the game with two catches for 29 yards.
He had 104 receptions in 16 games in 2019. This season, he has caught 32 passes for 327 yards. He was expected to be a larger part of the offense with running back Austin Ekeler injured.