The notion of Gates coming back to the Chargers has been a popular one since fellow tight end Hunter Henry sustained a season-ending right ACL injury last week.
"I would always be excited if he walked back in the door, obviously," Rivers said about Gates. "But that's something that Tom [Telesco, general manager], John [Spanos, president of football operations] and Coach [Anthony Lynn] -- all of those guys I'm sure would discuss and see about bringing anybody in for that matter. But certainly he would get my vote."
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 organized team activities on Tuesday.
Rivers said he talked with Gates about a possible return.
"I have talked to him, and I'll kind of leave that between us," the 36-year-old Rivers said. "He first, like I said, he hated it for Hunter. If something were to happen down the road, he wouldn't have wanted it to come that way, with Hunter's absence. So that was really more of our conversation.
"But he's doing good. I think this time of year for him, even in these last few years of his career, I don't know if he's doing a ton different than he was. He stayed ready. He wasn't here this time of year a ton. He was always getting himself ready and with his family and children. So I'm sure he's in shape and will be ready if called on, if that's something he's interested in."
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 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. Green has 71 catches for 807 yards and four touchdowns during his seven-year NFL career.