Tennessee Titans general manager Jon Robinson announced Wednesday that the team has signed quarterback Trevor Smith to a one-year, $2.5 million contract.
The team is also adding veteran tight end Jake Coker, linebacker Brandon Magee and safety Tyquan Lewis to the roster.
Siemian, 24, has appeared in five games with the Titans this season and has thrown for 6,955 yards, 23 touchdowns and just four interceptions.
He has completed 64.2 percent of his passes and thrown 15 touchdowns against five interceptions.
The Titans have lost quarterback Ryan Fitzpatrick to a broken collarbone.
He threw for 3,066 yards and 12 touchdowns in 2016, and threw for 8,749 yards and 27 touchdowns in 2015.