After opening the 2016 season as the San Francisco 49ers' starting quarterback, Gabbert ceded the job to Colin Kaepernick five weeks later, finishing the season with a 68.4 passer rating, with 5 touchdowns and 6 interceptions.
Gabbert, 27, has spent three seasons each with the Jacksonville Jaguars and the Niners. He started 13 games in San Francisco over the past two seasons, winning four of them.
Jacksonville traded Gabbert, the No. 10 pick in the 2011 draft, to the Niners in 2014. With the Jaguars, Gabbert was 5-22 as a starter and threw 22 touchdown passes and 24 interceptions in 28 career games.
ESPN's Nick Wagoner contributed to this report.