Rooney has never made any secret of his antipathy for the Anfield outfit.
A boyhood Evertonian, Liverpool were always the enemy and after scoring the penalty which sealed United's record title triumph, Rooney shaved the number 19 into his chest hair.
However, he does recognise the revolution that has taken place under Kenny Dalglish.
Jordan Henderson and Charlie Adam have joined this summer, giving the Reds a British feel following the £35million arrival of Andy Carroll in January.
And while it might be 21 years since Liverpool last finished top, Rooney thinks they have the capability to end that run.
"I think Liverpool will challenge this time," he said.
"They have made some really good signings - British players - and, under Kenny Dalglish, I am sure they will be fighting harder than they ever have done to be up there.
"They will think they have a chance of winning the title."
Clearly, Rooney will be doing his utmost to stop that happening.
His hat-trick in Seattle on Wednesday was a pointer towards form that will be better than his tepid efforts for the first-half of last season.
"I don't set targets for myself but it would be nice if I can get through the season injury free," he said.
"It's always a big thing to get your pre-season under your belt because that is the main bulk of the work you get to do.
"We have trained very hard this week and we are looking forward to all the games."
Thanks to United's latest championship success and the ending of Manchester City's 35-year trophy drought in last term's FA Cup final, the Red Devils launch their new campaign against their near neighbours when they square up in the Community Shield at Wembley on August 7.
It already seems patently obvious the Blues represent a clear danger to the Red Devils' hopes of retaining their Premier League crown, which Rooney confirms is the number one priority this season.
But that cliched traditional curtain-raiser takes on added meaning purely because of the side United are going to face.
"When you play at a club like Manchester United, the goal is to win all the competitions," said Rooney.
"It is true our priority is to keep our Premier League title, but we won't ignore any competition.
"We want to win everything, starting with the Community Shield. There is nothing better than a derby to start the season."