Lukaku after struggling for game time at Old Trafford secured a move to Inter Milan where he won the Serie A title.
But the former Everton forward has completed a £97.5 million move from the San Siro to Chelsea and Souness believes the Red Devils will regret for offloading him considering his bright start to the season at Chelsea.
“I don’t think Manchester United should’ve ever let him go.
“He seemed unhappy when he was there, and he’s come back a happy man. He definitely is a key man. Goals change games. If you have someone who can nick goals then all of a sudden you’re a different team.
“He hasn’t got a weakness. I’m not saying he’s brilliant at everything but he’s got no obvious weakness. If you’re playing against him and you’re a centre-back you’re not going to enjoy it.
“I don’t think anyone will enjoy playing against him, he’s got a bit of everything in his game and he’ll be the difference for them should he stay fit.”
Despite Lukaku registering 42 goals in 96 matches over two seasons at Manchester United was still not considered as a key member into their system as he left for Inter Milan in 2019.
Lukaku has scored 3 goals in three Premier League appearances for Chelsea this season and is keen on making a statement at Stamford Bridge.
