Hull manager Nigel Pearson praised Nick Barmby after the veteran scored a minute after coming on as a substitute to send his team above Cardiff and into the top six of the Championship.
The 37-year-old player-coach netted the winner after 17-year-old substitute Joe Ralls had cancelled out Matty Fryatt's opener with his first senior goal.
Ralls was an early replacement for Kenny Miller, who hobbled off with a groin problem that could see him ruled out of Scotland's Euro 2012 qualifier with Liechtenstein next Saturday.
To compound a tough day for Cardiff, referee Colin Webster reversed a decision to award a penalty to the visitors just moments before Barmby's winner.
"Nick has always had a very positive impact for us," Pearson said. "He is a player who brings quality to the team.
"We're not just a squad of young players but our young players have great potential, and Nick is a role model for them.
"During the week he's more of a player than a coach, but this is his club and it means a lot to him.
"The most important thing for me is that I know he can still perform. He's not just a cosmetic extra."
Hull, who ended Cardiff's six-match unbeaten run, have now avoided defeat in their last six matches themselves.
"There are lots of teams that will think they have a chance, but we've made some great progress," Pearson said.
"The players can be very pleased with their performance and there is an air of confidence about them."
Cardiff felt aggrieved after referee Webster performed a U-turn on a decision to award a penalty to the visitors after Jack Hobbs' trip on Filip Kiss.
The referee, after consulting his assistant, signalled for offside, and Barmby notched the winner moments later.
"He was clearly offside so it wasn't a fractional thing," Pearson added. "Common-sense prevailed and it would have been unjust to have conceded at that point."
However, Mackay was dismayed by what he called a "game-changing decision".
He added: "The linesman has apologised for not putting his flag up, but that makes no difference to me. The play went on into a second phase and if it was offside it was marginal."
The penalty controversy marked a bad day for Cardiff, who had to reshuffle following Miller's early injury.
"He suffered a groin problem in the first minute and we had to restructure and put square pegs in round holes," Mackay added.
"But I thought we were good enough value to get something out of the game."