The mercurial fly-half has since signed a new deal with the ARU but only time will tell if he has put his off-field problems and injury worries behind him.
Wallaby skipper Horwill has been impressed with his team-mate's pre-season commitment with the Reds, though, and he remains convinced 2013 will be a big year for Cooper.
"You let your actions do the talking and Quade's very big on that," said Horwill.
"Any time you have injuries and interruptions to your year it's frustrating and that happened to him obviously last year and he might have struggled with that a bit.
"But he's been fit, he's been training, he's been running, doing everything, and you can see that he's really enjoying being out there, so I'm expecting Quade to be Quade and do what he does best.
"He needs to make sure he keeps performing the way we all know he can because he is a world-class player and someone who's got some freakish ability that a lot of people in the world would be pretty envious of.
"Quade's been excellent (in pre-season), he hasn't missed a session, he's trained extremely hard and he's in very good shape physically.
"For us at the Reds he's always been the guy that's always turned up and been very proud and worked hard to play for Queensland, so I can't fault him in that sense."
Cooper is all set for his first competitive fixture since having knee surgery after the Wallabies' narrow win at home to Argentina in mid-September but Horwill won't be joining him in Reds side to face the Brumbies this weekend.
Horwill was due to return from an eight-and-a-half month lay off with hamstring problems last week but a minor ankle injury prevented him from featuring in the Reds' final trial match.
And despite Brumbies boss Jake White claiming that the opposition were playing mind games and that the second row would feature in Canberra on Saturday, Horwill insists he definitely won't be available for the opening round of Super Rugby action.
"The ankle is not good enough to play so I'm not running out this weekend, but hopefully I will be right to play a part of the game against NSW (a week on Saturday),'' added Horwill.
"It's a little bit frustrating obviously with the long lay-off that we've had and everything was sort of tracking the way we had planned it but, unfortunately, a little hiccup happened. That's sport, so I've just got to get the ankle better and get back as soon as I can.
"The hamstring's been really good. We did a lot of stuff to really test it out and check that it can withstand what it needs too.
"I'm happy with my fitness, obviously there's no duplicate for match fitness so I might be a bit short of a run.
"Going into the season is obviously not ideal but it's the cards we've been dealt so we've just got to get on with it and do what we can."