The 25-year-old has been recalled to the squad for this weekend's clash against arch-rivals Australia but, in his absence, Beauden Barrett and Colin Slade have filled in admirably at No.10.
And although Cruden's indiscretions will not be held against him, Foster insists the playmaker has put himself behind the eight-ball.
"As far as we're concerned Cruden has done his time so we move on, but in the All Black environment it's one thing to do your time but you also give someone else an opportunity," Foster told Radio Sport.
"Beaudy has had a couple of starts and we think he's done a pretty good job of it, so Aaron is going to have to come in and train well and train hard and just knuckle down and get back into the system.
"He has to come to terms with what we've actually done for the last couple of test matches since he's been away. He'll go back to a learning curve.
"And I'm sure that Beaudy will be pretty keen on progressing on the two starts that he's had so it's going to be pretty good competition.
"The likes of Sladey have also been very impressive in our environment - I've been very impressed with how Sladey has settled in and handled a lot of different jobs.
"He's got a skill-set that also complements Beaudy and Aaron in terms of off the bench."