Sanchez’s former club Arsenal spent the day assuming responsibility for the 29-year-old inadvertently missing a drugs test on Monday, as he dealt with the logistics of his United transfer.

The striker himself ended the night by ensuring manager Jose Mourinho tasted victory on his 55th birthday and the occasion of his 100th match at the United helm.

Sanchez dropped deep too often and conceded possession cheaply too frequently in a mixed first half, but still posed United’s chief threat on his Red Devils debut.

That spark generated the wholly-dominant visitors’ first two goals on a night where Darren Way’s Yeovil had precious few opportunities to upset the odds.

Sanchez may have to answer questions from UK Anti-Doping over Monday’s missed drugs test, but is already offering the answers for new club United.

Arsenal boss Arsene Wenger insisted the Gunners must take the blame for the mix-up that led to Sanchez missing Monday’s random drugs test at the London club’s training ground.

United will no doubt expect to clear up the issue with little fuss however, and boss Mourinho will surely be content with his new recruit’s first club outing.

United coasted through a low-key first half, where Yeovil missed two solid chances.

First Jordan Green had a shot rebuffed after sneaking through on the inside left, before the unmarked Omar Sowunmi headed straight at Sergio Romero from a free-kick.

Eventually the visitors found something approaching fluency, with Herrera losing the ball cheaply in the Yeovil box from a promising attack.

Sanchez threaded a fine ball to Scott McTominay, but the young midfielder saw his low effort turned around the post by Artur Krysiak.

When United finally did move in front, the Red Devils pounced on Thomas James’ misstep.

The defender thought he was free to clear after the ball escaped Rashford in the Yeovil box. The England forward had not given up the ghost however, and nipped in before dinking over the onrushing Krysiak and home for the lead.

Sanchez had fed Rashford in a smart pass in the build-up to the opener, finally conjuring an incisive ball after a sequence of misplaced passes.

And so United took a 1-0 lead into the break, barely breaking sweat in the process.

United killed the game on the hour with a clinical break, Juan Mata feeding Sanchez and the Chile forward playing in Herrera, who fired home without issue.

Mata had the ball in the net just minutes later, but the tap-in was ruled out for offside.

United were already home and hosed by the time Lingard raced through and drilled the third, as Yeovil fell off the pace at the death.

Substitute Lukaku tapped in the fourth into an empty net, as United finished off the hosts in style.

In the night’s other FA Cup clash Atdhe Nuhiu scored twice as Sheffield Wednesday beat Reading 3-1 to advance to the fifth round.

George Boyd was also on target for the hosts with substitute Sam Smith scoring a late consolation for Reading.