United left-back Luke Shaw opened the scoring with a volley that scraped Jesse Lingard’s back as it bounced over the Derby defence and into the far corner, before Ighalo’s brace sealed a quarter-final spot for Solskjaer’s side.
Ighalo’s first goal saw the striker hammer a rebound into the roof of the net, before he capitalised on a loose ball in the box for his second.
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“When you get strikers in you want them to be happy and confident,” Solskjaer told the BBC after the game. “He has come in here and of course we still have a few injuries and it is great for us to have Odion to call upon.
“He is a different striker for us and scores some good goals, there is not many who could dig that one out for his first.”
Solskjaer also praised United’s record goalscorer Wayne Rooney, who lined up for Derby on Thursday evening.
“Everyone loves Wayne, all the supporters at Manchester United appreciate what he did,” Solskjaer said.
“He played well. He shows class and sometimes he has too much time on the ball for my liking.”
United’s FA Cup quarter-final sees them travel to Norwich.