The Chilean looked all set to join Manchester City this month after entering the final six months of his Gunners contract.

But United swooped to gazump their local rivals and wrapped up a swap deal that saw Henrikh Mkhitaryan go in the opposite direction.

Sanchez has been hailed as the kind of player United need to close the gap on Pep Guardiola's all-conquering City.

And the 29-year-old was offered the chance to show his quality tonight when Jose Mourinho handed him his debut in the Red Devils' FA Cup showdown with Yeovil.

Sanchez provided glimpses of the talent that have seen him talked up as one of the Premier League's elite stars.

And Herrera almost sounded in awe of the former Barcelona man while discussing him after the game at Huish Park.

"Alexis Sanchez can play everywhere, he's fantastic," he said. 

"The attitude he shows, he fights for every ball. 

"He's a star and it's amazing to have him with us."

Sanchez will make his Premier League bow for United when he lines up against Tottenham on Wednesday night.