In 2015, there was some media speculation that the Los Angeles Chargers (The San Diego Chargers back then) could’ve possibly traded Rivers to the Titans in exchange for the second overall pick in the 2015 NFL Draft, which they would presumably use to select Mariota.
Clearly, that never materialized.
Four-and-a-half years later, Rivers is in the final year of his contract with the Chargers, and after 15 seasons with the franchise, the Chargers could end up letting him enter free agency.
Chargers general manager Tom Telesco did speak highly of Rivers after the 2019 NFL draft.
That being said, sometimes things change, and the Chargers could decide ultimately to move on from him after this season.
Rivers would not be a long-term solution to the quarterback issue; he turns 38 this December and for all intents and purposes, he might not even be available, but I think it would be a good option for the Titans to at least inquire about his services. He could possibly be a stop-gap QB while the Titans either groom a rookie QB or wait until 2021 to draft one.