That process could begin at this year's NFL draft, with the Chargers reportedly doing their homework on players like Missouri's Drew Lock and West Virginia's Will Grier, according to Ian Rapoport of NFL.com:
Rapoport did note that the Chargers were committed to Rivers as their starting quarterback and said he wouldn't be surprised if they spoke about a contract extension soon, with Rivers entering the last year of his deal. But having a young quarterback in place for Rivers to mentor makes sense.
Andrew Siciliano of the NFL Network previously reported that the Chargers had met with Lock and Duke's Daniel Jones:
Rivers had one of the best seasons of his career in 2018, throwing for 4,308 yards, 32 touchdowns and 12 interceptions while completing 68.3 percent of his passes. He led the Chargers to a 12-4 record and a 23-17 win over the Baltimore Ravens in the Wild Card Round of the AFC playoffs before bowing out the next week to the New England Patriots in a 41-28 loss.
Pro Football Focus gave him a grade of 89.9 for his efforts, seventh among quarterbacks. So there's little indication that Rivers is slowing down anytime soon.
But nobody can play forever, and there's a chance a solid quarterback could fall to the Chargers at No. 28. Kyler Murray will likely be off the board by then, but after that, it's unclear where the quarterbacks will fall, and in what order. Alongside players like Lock, Grier and Jones, Ohio State's Dwayne Haskins is another player to keep an eye on in the first round.
In his March 25 mock draft, B/R's Matt Miller had Murray going No. 1 to the Arizona Cardinals, Haskins going No. 6 to the New York Giants, Lock going No. 10 to the Denver Broncos and Jones going No. 15 to Washington. That would leave a player like Grier available for the Chargers should they choose to go in that direction.