The Vikings are in need of a No. 2 quarterback behind Kirk Cousins.
Mannion is an unrestricted free agent and won’t return to the Rams, who signed Blake Bortles this week.
Mannion, who turns 27 next month, has played 10 games with one start in his career. He did not earn much confidence from the Rams with his 2018 preseason performance, completing 52.2 percent of his passes for 168 yards with a touchdown and two interceptions in three games.
The Rams made him a third-round pick in 2015.
The Vikings dealt a fifth-round pick to the Broncos last March for Siemian, who didn’t play a single down in 2018.
Minnesota reportedly wants him back, but the Vikings are cap-strapped, and Siemian has interest from a few places, according to Garafolo.
Siemian started 24 of 25 games players over a two-year stretch as a starter for Denver. He completed 59.3 percent of his passes for 5,686 yards with 30 touchdowns and 24 interceptions.