Henry, who was expected to be a focal point of the Chargers' offense in 2018, injured his right knee while running downfield on the first day of OTAs on Tuesday. The 23-year-old is expected to get a second opinion on Wednesday, although the likely scenario has him done for the season, per multiple media reports.
The transition from Gates to Henry started in 2016 when the club used a second-round pick on the Arkansas product. Henry recorded 45 receptions for 579 yards and four touchdowns in 14 games in 2017 before a lacerated kidney ended his season.
Considered a lock for the Pro Football Hall of Fame, Gates had a reduced role with the Chargers in 2017, playing 478 snaps and making 30 receptions for 316 receiving yards and three touchdowns.
Gates, 37, hadn't had fewer than 49 catches in a season since recording 30 as a rookie.
An eight-time Pro Bowl selection and three-time All-Pro, Gates is the Chargers' all-time leader in receptions (927), receiving yards (11,508) and touchdowns (114), with his touchdown total an NFL record for tight ends.
Gates has caught 87 touchdown passes from Philip Rivers, the most in league history for a quarterback-tight end tandem.
He also has 21 games in his career with more than 100 receiving yards, one of only seven tight ends to achieve that feat.
Virgil Green, who is more of a blocking tight end, was signed to a three-year, $8.6 million deal this offseason. He joins Sean Culkin, Ben Johnson and Cole Hunt as the other tight ends on the team's 90-man roster.