“The guys worked hard, but just weren’t able to get back,” Quinn said.
Ishmael, a valuable reserve and special-teams player, played 310 defensive snaps (34.1 percent) and helped the team through a rash of injuries at the linebacker spot.
Sharrod Neaseman will take over Ishmael’s roles on special teams.
With Collins out, cornerbacks C.J. Goodwin and Deji Olatoye will split his playing time.
Practice-squad quarterback Matt Simms did a good job in practice simulating 49ers quarterback Colin Kaepernick’s mobility.
“It’s a challenge, the speed that Kap plays with,” Quinn said.
The Falcons are tied for first place in the NFC South with Tampa Bay.
“It’s been a good week for our team, with the mindset, the attitude and the focus to get better,” Quinn said.