Arsenal boss Unai Emery is wary of facing a motivated Alexis Sanchez in tonight's FA Cup showdown with Manchester United.

Emery revealed ahead of Friday's FA Cup fourth-round clash that he tried to sign former Arsenal star Sanchez for Paris Saint-Germain in 2017 before the Chilean joined United last January.

"I respect him," Emery said of the 30-year-old forward, who is likely to receive a hostile welcome from Arsenal fans after his acrimonious exit 12 months ago.

"I don't know why his performances or quality is better or worse in these circumstances. Now, in the last matches, they are playing very, very well with very big performances.

"He's been starting on the bench after an injury but if he plays, we need to work to stop him because he is a very good player. Now, this team is different. I don't know why. They are playing with more confidence.

"They are winning their last matches and whether he is playing with one player or another player, they are with big performances.

"Alexis is a very good player and when I was at PSG, we thought he could help us."