Chelsea defender Gary Cahill has been impressed with the way Romelu Lukaku has improved since his unsuccessful stint at Chelsea, saying he's turned into a 'world-class striker.'

Lukaku joined the Blues back in 2011 when he was just 18-years-old. Unable to break into the team, he was loaned out to West Bromwich Albion and later Everton. His impressive run with the latter saw him secure a permanent move in 2014. 

Cahill, who had played alongside a younger Lukaku, admitted it was a difficult time for the Belgian at Chelsea.

"It’ll be difficult. I’ve played against him and trained against him loads of times," Cahill, who will face Lukaku in the FA Cup final at Wembley on Saturday, said at Cobham Training Centre, as quoted by Goal.

 "The cup final’s going to be whoever performs on the day. We’ve put the season to bed and we have a full week to prepare in the right way. When he was here he had talent but he was very young. He’s developed into a world-class striker so credit to him. Sometimes when you’re at a club like Chelsea you feel sorry when you see a player move on, because naturally some progress and some don’t. You don’t hear about the ones that don’t."

"What everyone can see - pace, power, strength and he can finish. His goalscoring record is very good. But we’re not focusing on one player in this team. First and foremost, we’re focused on what we’re trying to do, and be respectful of the fact that they have numerous players who can turn a game on its head, as do we."

After failing to secure Champions League football,  Chelsea would hope to give something positive to the fans. Manchester United, on the other hand, have fared a lot better than their Saturday rivals, but would still need a trophy to legitimise their season.