Washington tendered Allen a contract last week, so he was expected to return.
Allen, 25, signed on with the Panthers as an undrafted free agent back in 2018. Allen was waived coming out of the preseason before the Panthers added him to their practice squad before being promoted late in the season.
The Panthers re-signed Allen to a one-year contract last offseason, but later traded him to Washington for a fifth-round pick. Allen was placed on the injured reserve list after undergoing surgery for a dislocated ankle in November.
In 2020, Allen appeared in four games for Washington and completed 69 percent of his passes for 610 yards, four touchdowns and one interception. He also rushed for 26 yards and a touchdown.