A Luke Brattan thunderbolt in the dying stages of the match proved the difference as the Roar ran out 2-1 winners against a side which the Brisbane coach picked for a top four finish.
Mulvey also made it clear he was unhappy with Melbourne Victory's handling of the announcement of Besart Berisha's end-of-season transfer between the clubs; news which proved a distraction in the build up to the Phoenix game.
"Let me tell you this; Wellington Phoenix are top four material, and we've beaten them three times this year," Mulvey said.
"That's the magnitude of this result.
"They've been playing ever so well lately, and Ernie's got them really aggressive.
"And they gave us some problems, they could have been two up at half time.
"But then we came back into just towards the end of the first half.
"I just loved that second half, it was fantastic," he said.
"That's what football's about for me.
"We went for it, I thought we played very well, we got the goals and the crowd got involved, brilliant stuff."
"I believe there's an offer from Borussia Monchengladbach," Mulvey quipped when questioned about Clut's performance.
"No, look, I was really pleased for Devante, he was blowing the big ones after about 65 minutes, but we got him off just in time.
"But absolutely delighted for the boy because he's trained with us probably since July with the first team and he worked his socks off inmidfield.
"I told him (he would be starting) about an hour and a half before kick-off.
"I thought that would probably be the best thing to do for him, and then he did the rest."
Reiterating comments he had made pre-match, Mulvey was also critical of Victory's decision to go public with the signing of Berisha mid-week.
"It's been a bit of a circus this week and I didn't appreciate the fact that it was in the public domain on Wednesday because we had a game to prepare for on the Friday.
"So I didn't think there was much respect shown to us."
