'I think they are very unsafe, Firmino works very hard to win the ball back and they have a lot of pace, ' Rooney told Sky Sports.
To white Rooney replied: "You'd think so". "He has got aggression, passion, desire".
I think he is (in a place where he can thrive),<blockquote>I've seen it last season in training a lot, he's a very talented player.
Wayne Rooney believes it would be "difficult" for Liverpool's front three of Mohamed Salah, Roberto Firmino and Sadio Mane to emulate Manchester United's attacking trio which included Cristiano Ronaldo, Carlos Tevez and himself.
"I think Ruud was used to David Beckham and Ryan Giggs getting the ball down, putting crosses into the box, getting on the end of them. You can see they're well on the way to doing that".
That is what Manchester United have really lacked - players around Lukaku who can really push Lukaku on. He's a bit like Harry Kane, he just wants to score. He is that good.
"The difference we had is Premier League winners" medals.
"His mentality - it hurts him when you don't win and you can't say that about all the players. If England are going to do well this summer it's on how well he does".
The former Barcelona forward scored his first goal for United in the 2-0 win over Huddersfield at Old Trafford on 3 February, and Rooney said his former club had recruited the "perfect player" to take them to the next level. He was one of the, if not the main, reasons we won the league that year.
For Everton, Rooney was an unused substitute as the Toffees were thrashed 5-1 at Arsenal on Saturday, and he said he found it painful viewing.