NFL teams are able to begin negotiations with the agents of soon-to-be free agents. However, contracts cannot be officially signed until Thursday at 1 p.m. Pacific.
The 49ers do not have any quarterbacks under contract for the 2017 season. Colin Kaepernick has officially opted out of the remaining year of his contract with the 49ers and will hit free agency on Thursday. No other 49ers quarterback was signed beyond the 2016 season.
Glennon, who was drafted out of NC State in the third round of the 2013 NFL Draft, has 18 starts and has played in 21 games over his four-year pro career. He has passed for 4,100 yards, 30 touchdowns, and 15 interceptions during that time.
Glennon's best year was his 2013 rookie season where he passed for 2,608 yards, 19 touchdowns, and nine interceptions through 13 games.
During that rookie season, Glennon replaced quarterback Josh Freeman after the Buccaneers started 0-3. Glennon went on to lose his first five starts before winning four of his next five. However, he finished out the season losing three straight. Glennon went on to be named to the Pro Football Writer's Association's All-Rookie Team for his 2013 performance.
The next season, Glennon lost his starting job to newly-signed quarterback Josh McCown. Due to an injury to McCown, Glennon went on to start five games for Tampa Bay in 2014 – winning just one.