"It was a steep learning curve and I think what he did in this season alone is somewhat of a miracle...that tells you what kind of smart, great athlete he is to even make it on to the roster of the 49ers or any other NFL team. I know the Seahawks like him an awful lot.
"The 49ers have no reason not to keep him (but) the smart thing on their part is find out what the hell he can do. He's come a long way from where he was at the beginning of the season. He's showed some great promise and has the attitude to work hard in the off season."
Barr said coaches and players backed Hayne.
"If he stays with the organisation and even if he doesn't - he could go over and be with another team - he will have a spot in the national football league.
"At this point, from what I've seen of his capabilities and what I've heard from coaches and team mates, they think he has capabilities to play in this league. So it will be fun to watch him grow in the NFL."
Barr is friends with Peyton Manning, the star veteran quarterback with Denver who has been linked by Al Jazeera with performance enhancing drugs.
Barr suggested to Radio Sport that Al Jazeera may be naive in the area of sports investigations, and he said that Manning was clean.
Barr said: I was about as angry as he was...I've known him since he was two years old and known the family really well this is something not in character with the name Manning.
"His wife has had some medical situations and I wont talk about that. To think he would jeopardise a Hall of Fame career...
"I think about what he stands for, his image..the reaction has been unified across football. I don't believe it at all. Some things are in play I can't talk about. "Al Jazeera is a new kid on the block when it comes to doing documentaries, particularly in sports. They may have been out of their element. When you've been in the business so many years...I just did not come away with confidence from what I heard. He's threatening to sue and I hope that he does."
Meanwhile Al Jazeera is standing by its story, but has made moves to emphasise what it actually said about Manning, USA Today reports.
Investigative reporter Deborah Davies said: "The only allegation in the program from (pharmacist) Charlie Sly is that growth hormone was sent repeatedly from Guyer (Institute) to Ashley Manning in Florida. We're not making the allegation against Peyton Manning."