Hussain said that the controversial decisions should take nothing away from a phenomenal performance by debutant Agar, who shared a Test record last-wicket stand of 163 with Phil Hughes.
"I thought it was a remarkable story," said the former England captain. "He played properly. We saw Tino Best score 95 against England last year but he played a bit like a tail-ender, just smashing it, but Agar just didn't look like a number 11 to be honest.
"He stunned England. At no stage would they have tried to work out how to bowl to Agar because they won't have seen him play. They have done now and he could end up a really, really good batsman and a very good all-rounder for Australia.
"He seized the initiative. The coach, Darren Lehmann, has told his players to go out there and be positive and England went on the defensive too early and immediately alleviated the pressure. Finn bowled a poor spell when he went short to Agar without men back.
"In the end the plan was right when Broad came on. It's fine going short at someone like that but you need to put a short leg in and three men out on the hook and that's how he got out on 98. Cook didn't have his best hour as captain at that point."
Fellow Sky Sports commentator Andrew Strauss also paid tribute to Agar, adding: "At 117-9 Australia were dead and buried but incredibly they managed to resurrect themselves through a fantastic partnership from Agar and Phil Hughes.
"We knew nothing about Agar's batting or his bowling yesterday but today he's looked nothing like a No 11 and has played some fantastic shots.
"Both of them played Graeme Swann very well in particular, even though with two left-handers in there you are almost expecting him to get them out.
"Agar took the game to Swann and as a left-hander that's not easy to do but he showed some deft touches, too - he showed that he wasn't a one-trick pony."
