The Switzerland international’s two-goal 20-minute cameo spared the blushes of goalkeeper Alisson Becker, whose 33rd-minute howler had gifted Jesse Lingard an equaliser the visitors barely deserved.

It was indicative of the mentality of the two managers that Mourinho sent on defensive midfielder Marouane Fellaini at half-time with the score at 1-1 while Reds boss Jurgen Klopp turned to Shaqiri when that scoreline had not changed midway through the second half.

That proved to be the masterstroke as he scored twice, both via deflections, to add to Sadio Mane’s 24th-minute opener as Liverpool beat United  for the first time in nine league meetings.

Even with a game to chase Mourinho decided £89million midfielder Paul Pogba was not part of the solution as the French World Cup-winner was an unused substitute.

The goals United conceded meant they have let in more in 17 matches (29) than they did in whole of last season and trail leaders Liverpool by 19 points – they are 11 off the top four.

Liverpool’s high-intensity start was such that it almost seemed they could take and use possession at will as even when United – who started with a back three which quickly became a back five – had the ball, which was infrequent in the first half, the Reds won it back with ease.

It was no exaggeration to suggest they could have had three or four in the first half, which they finished having managed 15 shots but scored only once.

Roberto Firmino was at the centre of Liverpool’s maelstrom, hustling and harrying opposition players while delivering cutting interventions going forward.

The Brazil international started and finished a move in the second minute which saw Victor Lindelof scrambling to deflect his shot behind.

United thought they had stunned Anfield into silence when Ashley Young’s inswinging free-kick from the left went straight in at the far post but an offside Romelu Lukaku had tried to play it on its way through and he was rightly flagged.

Two more chances fell to Firmino as the red tide continued to crash against a dark blue wall, with Mohamed Salah going down in the six-yard area scramble to collect the rebound.

Young cleared a Dejan Lovren effort off the line and Firmino shot over – the ninth attempt inside 20 minutes – before the breakthrough was made.

Former United defender Gary Neville said his old side were “all over the place…like spaghetti bolognese” and Mourinho’s players managed to get themselves in a tangle in the 24th minute.

No one closed down midfielder Fabinho, excellent both defensively and going forward, and his measured clipped pass was chest-controlled by Mane who then cleverly allowed the ball to drop low enough for him to volley it between De Gea’s legs.

Lovren should have made it 2-0 but fired over from six yards before Alisson gifted the visitors an equaliser when he spilled Lukaku’s cross into the path of Lingard, who gratefully accepted six yards out.

Lukaku’s lack of sharpness – he was dominated by Virgil Van Dijk in the air and over the ground – almost cost him dearly as he tried to compensate for a loss of control over-stretching and clattered into Naby Keita, for which he was booked.

Mourinho had seen enough and sent on Fellaini in central midfield for wing-back Diogo Dalot at half-time as he reverted to a back four.

It did little to change the momentum as Firmino’s toe-poke was parried by De Gea with the goalkeeper and Young blocking Keita’s follow-up, while Lovren had a header deflected wide.

Three minutes after coming on Shaqiri struck, his shot rifling in off the crossbar with the help of a Young deflection.

He was not finished there, seizing on a Firmino backheel meant for Salah to fire past De Gea, this time with the aid of a deflection off Eric Bailly.

Television cameras turned to a grumpy-looking United chief executive Ed Woodward alongside an equally unimpressed United great Sir Bobby Charlton as Liverpool supporters chanted ‘Don’t sack Mourinho’.

- Press Association