Ole Gunnar Solskjaer is wary of the threat Wayne Rooney poses to Manchester United's FA Cup hopes as the Derby forward looks to prove there is "still fight in an old dog".

The Old Trafford giants, on an eight-match unbeaten run in all competitions, head to Pride Park on Thursday for a fifth-round tie that will pit them against their all-time top-scorer.

Rooney scored a club-record 253 goals across 559 appearances during a trophy-laden spell at United between 2004 and 2017, when he returned to boyhood club Everton before a spell with Major League Soccer outfit DC United.

The 34-year-old returned to home soil to join Championship side Derby as player-coach at the end of last year and is now preparing to line up against his former club. "He gave absolutely everything for this club and we all appreciate that," Solskjaer said. "But any goal he scores against us will be chalked off his goal tally! He doesn't want to score too many of them.

"He's a threat, in and around the box, set plays, and of course this game Wayne will show what he can do and he wants to prove that there's still fight in an old dog. We've got to be on our toes, don't give him any space in and around the box or in midfield."

"At the latter end when he played in midfielder, you can see he's got Scholesy-like passing range," he added, in reference to former United midfielder Paul Scholes.

Solskjaer was asked whether England's all-time top scorer was under-appreciated in some quarters but said that was not the case. "He's been a fantastic player for Man United and he played here for so long, he's the club's top scorer, he's won so many trophies," said the Norwegian boss.

"For me, I don't think the fans underrated him. I think everyone really, really appreciates what he did for us. He's still very welcome, he's still around the place, he still comes to Old Trafford. He will get a good reception from our away fans in that game definitely."