Chargers tight end Hunter Henry suffered an ACL injury during the first organized team activity of the summer, the team announced Tuesday.
The news was first reported by ESPN's Adam Schefter.
According to Schefter, the injury occurred while Henry was running downfield and he was untouched. He will have a second opinion on Wednesday, but the injury is believed to be season ending.
The 23-year-old had 45 receptions for 579 yards and four touchdowns in 14 games during the 2017 season, accruing 100 more yards than his rookie season in 2016, but halving his touchdown total in a season cut short by a kidney laceration.
The injury is a big blow to the Chargers, who moved on from long-time starter Antonio Gates at the end of last season and expected Henry to continue his maturation into one of the league's top young tight ends.