Zlatan Ibrahimovic's first Manchester United hat trick saw off St Etienne as Jose Mourinho's men took control of this Europa League round-of-32 tie.
The build-up to the Old Trafford encounter was dominated by Paul Pogba's meeting with his brother Florentin Pogba, but Ibrahimovic stole the show as he took his tally for the season to 23 with three goals as United eventually saw off their French opponents to win 3-0.
St Etienne had flustered United in the early stages of this first leg but the hosts went ahead through a fortuitous Ibrahimovic free kick -- both in terms of its award and the way it deflected home off Vincent Pajot.
Paul Pogba, with his family watching from the stands, performed impressively as United improved after the break and hit the bar with a close-range header.
But this was to be Ibrahimovic's night as he turned home at the far post and then fired home a late penalty to take his tally against St Etienne to 17 goals in 14 matches.
The three-goal margin should allow Mourinho to rotate his side in France next week ahead of the EFL Cup final against Southampton days later.
There promises to be quite the atmosphere in Saint-Etienne if Les Verts' raucous travelling support is anything to go by, although their use of flares will no doubt lead to sanctions from UEFA.
It meant the ground was filled with smoke at kick-off, but visibility was not reduced enough to explain Eric Bailly's shaky start.
The young defender's blushes were spared from a poor pass, only to then ignore Ander and attempt a ball back to Sergio Romero. That decision was telegraphed by Romain Hamouma, who jinked past United's back-up goalkeeper only for his cross to be hacked clear.
United heeded their manager's request to calm down and began to threaten to score rather than shoot themselves in the foot.
Marouane Fellaini saw a goal ruled out and Anthony Martial forced Stephane Ruffier into a smart save, but there was little the goalkeeper could do from the free kick that soon followed.
Ibrahimovic appeared fortunate to get the call in his favour after a tussle with Jordan Veretout. The veteran tried to direct the resulting set piece under the wall, with the cheeky attempt taking a deflection off Pajot and wrong-footing Ruffier.
St Etienne claimed they should have had the chance to immediately level from the spot, but no penalty was awarded after Jorge Intima tangled with Daley Blind.
Juan Mata was twice denied after meeting Paul Pogba's smart clipped pass, with Ruffier doing well again to thwart Martial at the end of a mazy run. Ibrahimovic, unable to rearrange his footing, turned over the rebound.
Henri Saivet, Hamouma, Florentin Pogba and Kevin Monnet-Paquet tried to level the scoreline as a thundering first half came to a close.
Play resumed frenetically as Ibrahimovic saw a header chalked off for offside, before Paul Pogba missed the target and Ruffier stopped Martial and Ibrahimovic in quick succession.
Herrera will miss the second leg after receiving a booking following Antonio Valencia and Paul Pogba chances, with the latter then sending a header off the crossbar.
Nolan Roux failed to capitalise on that missed opportunity after being put through by Ole Selnaes, allowing United to move out of sight.
Substitute Marcus Rashford did well to get to the byline minutes later and his low cross was turned in at the far post by Ibrahimovic.
Jesse Lingard curled wide from edge of the box and two minutes from time United had a third.
Ibrahimovic went down in the box and the Swede dusted himself down to slot home. Paul Pogba sent a late free kick close but the headlines belonged to his teammate.