Former Liverpool goalkeeper Brad Friedel has issued a warning to his former club over Cristiano Ronaldo's threat ahead of their Sunday clash.
The Portuguese talisman has an outstanding record for United against Liverpool during his career and throughout his previous stint at Old Trafford, the Merseyside club only got the better of him three times in the Premier League, one of which he wasn't in the team.
It will be the first clash between the two English giants since the 36-year-old made his return during the summer after signing from Juventus.
But Ronaldo will be looking to continue his startling form in all competitions and comes into the grudge match in red-hot form after scoring the winner against Atalanta.
"He doesn't even have to have a good game. He's changed the way he plays as he's got a little bit older but just look him at sometimes, he just drifts, he knows exactly when to make that run, the one-two, obviously has the tremendous strike on him," the former American international told Sky Sports News' Football Show.
"He's also big, strong, good in the air.
"These are also the types of the games, again don't be surprised, he only creates two chances in the game and scores both, that's why he is the world's best and this is a player Liverpool will need to keep their eye without a doubt. He is going to have chances to score in the game.
"Wouldn't you pin your hopes on him if you had him in your team? That's why you sign him. You hope he turns up on this day and scores a hat-trick for you, which he is capable of doing, it's not easy against Liverpool, it's one of the reasons you have him in the team.
"You better believe he'll be able to carve out a few chances but Liverpool have a strong back four and an outstanding goalkeeper, a fascinating contest. You can throw form out the window a little bit in this one because of the history the two clubs have."
The Liverpool manager Jurgen Klopp is well aware of the five-time Ballon d'Or winner and has previously stated that he is unhappy that the Portugal international returned to Old Trafford.
"Am I happy that he is at United? No, I can't say that," the German said last month.
"I was surprised, not about United, him going in there in the end, but when I first heard the rumours about him wanting to leave Juventus. I had no idea about that.
"I am not in the Juventus circle when people inform me from time to time about what is going on there, so I was surprised about that.
"He was going to City and I thought 'oh, that could be fun for United' and then, obviously, United stepped in and did it.
"It's all fine. It's a free world and they can do what they want."
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