Foster has been unable to play in a competitive match since returning to the Ibrox club this summer.
But the signing ban has now expired and the right-back could feature against Arbroath at Ibrox on Saturday.
Speaking to the Rangers website, he said: "Nothing prepares you the way games do and I know that when I play my first game I'm going to be pretty tired at the end of it.
"It's been difficult for the coaches to match the intensity you get in matches when we've been training.
"We've all just been doing the best we can. Hopefully once we play, we'll find ourselves getting fitter."