Foster suffered a dislocated ankle in Monday's 24-17 loss to the Buccaneers. The fourth-year Rutgers product has recorded 117 tackles, with six sacks, in 49 career games.
Ijalana -- the Colts' second-round pick in this year's draft -- injured his knee on Monday. He appeared in the first four games of the season, playing primarily on special teams.
Additionally on Wednesday, the Colts signed offensive tackles Michael Toudouze and Quinn Ojinnaka, elevated defensive tackle Ricardo Mathews from the practice squad and waived linebacker Nate Triplett. Offensive guard Jaimie Thomas -- already on injured reserve -- was suspended four games by the NFL due to violation of the anabolic steroid and related substances policy.