Ighalo has been in form for Watford this season with 14 league goals so far.

Ahead of the clash, Smalling says Ighalo and his partner, Troy Deeney are tough to handle.

In the reverse fixture at Vicarage Road, United won 2-1 with Deeney converting from the spot after Ighalo was fouled in the 18-yard box.

"They were a real handful last time," Smalling told the Daily Star.

"Not a lot of teams play with two up front and they're two guys who can run in behind the defence, hold the ball up, play it out and they can obviously both finish as well.

"They were a handful when we played against them and I've seen them play in the same way many times this season."

"Watford deserve full credit for going for it this season, attacking teams and not sitting behind the ball. They deserve to be where they are in the league table."