Based on initial tests, Allen suffered a suspected torn ACL during the second quarter of the game, NFL Network Insider Ian Rapoport reported. Allen was down on the field in pain before being carted off the field. The team confirmed that he suffered a right knee injury, but coach Mike McCoy said Allen he'll undergo further evaluation after the team returns to San Diego.
The fourth-year pass catcher looked sharp, and was consistently getting open against Chiefs cornerback Marcus Peters. With Allen, Danny Woodhead, Antonio Gates, new acquisition Travis Benjamin and a rejuvenated Melvin Gordon, San Diego's offense looked borderline unstoppable against a rock-solid Kansas City defense.
Allen suffered a lacerated kidney in Week 8 against the Ravens in 2015, and was placed on injured reserve. He was on pace for a monster season, accumulating 67 catches and 725 receiving yards at the season's halfway point.