The biggest rivalry in English football returns this Sunday as Liverpool travel to Old Trafford to face Manchester United—and the tension is already boiling over.

For the past decade, Liverpool have largely dominated this fixture, often arriving as clear favorites. But this time, the script has flipped. Arne Slot's Liverpool side currently sit 4th in the Premier League table, well below their usual sky-high standards. While they've managed three straight wins against Fulham, Everton, and Crystal Palace, the overall season has been a struggle for the defending champions.

On the other hand, Manchester United are flying high. Under interim manager Michael Carrick, who took over in January, United have lost just two of their last 12 matches—including statement victories over both Arsenal and Manchester City. Champions League football is all but secured, and the Red Devils are brimming with confidence.

Enter former Manchester United defender Paul Parker, who couldn't resist taking a playful but pointed jab at Liverpool boss Arne Slot ahead of the clash.

"The gap between the two clubs has certainly got closer, so thank you, Mr. Slot!" Parker said with a grin. "But even still, Liverpool haven't dropped anywhere near as far as what Manchester United did."

Parker didn't stop there. He warned that Liverpool's summer transfer window could be decisive—and not in a good way. "If they keep going like this, then who knows? But this summer is huge for them, because they need to sell more players again," he explained. "Like at Manchester United, you need a certain type of player to play for a club like Liverpool, because of the history and what it means."

That's a pointed reference to Liverpool's record-breaking £400 million spending spree last summer, which has yet to yield the expected returns. Several high-profile signings have struggled to find their footing, leaving Slot with a squad that's still finding its identity.

Parker also noted a telling shift in the mood among United fans. "At the moment, Manchester United fans haven't spoken too much about the game, which is strange because they're usually worried about being smashed!" he said. "Usually, Manchester United freshen themselves up for big games, like we saw against Manchester City and Arsenal."

With both clubs heading in different directions, Sunday's showdown at Old Trafford promises to be one of the most intriguing in recent memory. Will Liverpool rediscover their dominance, or will Manchester United prove the gap has truly closed? One thing's for sure: Paul Parker will be watching closely.