"It's been a massive year for him. He's done magnificently well in the Hurricanes environment. He's come in and had a couple of test matches and started a pretty big one and has done himself proud."
Uncapped Crusaders fullback David Havili, 22, has been called into the squad as Barrett's replacement. Havili impressed hugely in the No15 jersey this season for the Super Rugby champions, and the All Blacks are keen to get a closer look at him for his all-round skill-set as well as his ability to play in the midfield, if required.
"While he's a utility, he's stepped into that fullback role really well," Foster said.
"He's a reasonably experienced footballer now... he's played in a number of positions so he brings that to the table but he looks pretty settled at fullback. It's just nice to reward a player who has played his way in with form."
With Ben Smith missing the Rugby Championship following the first two tests against Australia, the first of which is in Sydney a week on Saturday, fullback is a position of intrigue for the All Blacks. Israel Dagg is obviously well qualified to play there but the selectors like him on the right wing these days, with Damian McKenzie also a possibility.
The All Blacks like Havili's kicking game and physicality when carrying the ball. He has also become far more accurate as a defender as he has become more used to playing at the back.
Havili and his Crusaders teammates were late arrivals for the camp in Auckland today due to fog in Christchurch, and none of them will take part in tomorrow night's "game of three halves" in Pukekohe.
Prop Owen Franks will continue to be monitored as far as his injured Achilles is concerned, Foster said, while the Blues players - not required to Super Rugby playoffs - will be looking forward to a hit-out against Counties and Taranaki.
Maintaining their skills under pressure will be the big improvement the coaches are looking for after a drawn test series against the Lions.
"We've certainly gone away and have done a lot of work on how we could have been better," Foster said. "And we've got to make sure we've learned some lessons and we do get better. Clearly we want to start well and the Sydney test has always been a massive starting point for us; playing an Aussie team that has been pretty well prepared for the last four weeks. We've got to go over and not compromise at all on our preparation to make sure we're ready.
"The lesson in the third test was we created what we needed to create and we weren't good enough to take it."
Foster confirmed Blues midfielder Sonny Bill Williams would also play for Counties B in a pre-season match on Saturday.