Former Manchester United winger Nani says a clash with fierce rivals Liverpool can propel Jose Mourinho's side to greater success in the Premier League.
Jurgen Klopp's high-octane side are one of the league's form teams on the back of four consecutive top-flight wins and will welcome United to Anfield on Monday looking to open up a six-point advantage over their rivals.
Nani - now at Valencia - enjoyed six wins over Liverpool in 11 contests as a United player, scoring once spectacularly in a 3-0 victory at Old Trafford in March 2008.
The Euro 2016 winner revealed the famous fixture's heightened sense of importance often gave Alex Ferguson's United an extra boost in their title charges.
"When you play that kind of game it gives you great motivation," the Portugal winger told Omnisport. "It pushes you in the league, it makes you stronger.
"Ferguson used to say that this is not just a game, it's a challenge.
"Everyone must win their battle against their opponent. We're not just playing, we're going out there to win.
"Win every ball, tackle, race, everything. Football comes last. We didn't always play beautiful but plays hard."
United boss Mourinho has overseen just one win in four Premier League games as what looked like an early title tilt has faded.
The Portuguese has three Premier League titles to his name, a tally bettered only by United legend Ferguson, who Nani ranks as the English game's most fearsome tactician.
He added: "100 per cent [Ferguson] is the greatest manager in Premier League.
"The way he works, the way he was with us. Not just because he wins all the trophies, the way he prepares, approaches each day and each game.
"He had the motivation and was strong when he needed to be. He could do the human side.
"I'm very happy to be part of his story, and happy he's part of mine. I will remember him always."