The 34-year-old quarterback appeared to suffer the injury when Donald beat Falcons left guard Wes Schweitzer, who was playing for James Carpenter. On the play, Ryan’s right ankle was severely twisted and he limped off the field.
Donald also stripped the ball from Ryan.
Ryan left the game having completed 16 of 27 passes for 159 yards and one interception. He had a passer rating of 60.6. He was replaced by backup Matt Schaub, who led the team on the following possession to the end zone.
Ryan, who signed a guaranteed $100 million, six-year extension last season, has not missed a game since being sidelined for two games with turf toe in 2009.