Manchester United fought back from two down to beat Newcastle and avert a defeat that would have cranked up the pressure on manager Jose Mourinho.
The hosts conceded twice in a lacklustre first 10 minutes, with Kenedy and Yoshinori Muto breezing in to score.
United briefly roused themselves with Marcus Rashford heading wide from five yards, but also needed David de Gea’s excellence to deny Muto his second and a potentially decisive third for the Magpies.
The hosts departed at the break to jeers – some of which were aimed at the club’s owner and executives, rather than the manager.
But by the final whistle, it was the name of Mourinho that rang around Old Trafford.
The Portuguese, who brought Alexis Sanchez, Juan Mata and Marouane Fellaini off the bench in pursuit of victory, saw his side reenergised after the break, when two of his three substitutes found the net.
As Newcastle dropped deeper, Mata swept home a free-kick with 20 minutes left to trigger an onslaught on the visiting goal.
Martial curled home six minutes later from Paul Pogba’s pass and, after goalkeeper Martin Dubravka pawed away Chris Smalling’s effort, Sanchez delivered the winner in the last minute of normal time, heading in Ashley Young’s cross.
According to one report on Saturday, the club hierarchy had decided before this game to get rid of Mourinho regardless of today’s result.
BBC Sport’s understanding is that Mourinho, in fact, still has the support of the club’s board.
Their faith might have been tested by an astonishing opening.
As chief executive Ed Woodward watched on grim-faced in the stands, United’s defence crumbled, conceding twice in the initial 10 minutes of a Premier League game for the first time.
First, a lunging Nemanja Matic failed to intercept in midfield before Young tamely allowed Kenedy to turn on to his favoured left foot and fire in.
Three minutes later, the hosts were either too uncertain or unwilling to close down Jonjo Shelvey, allowing him to sweep into the heart of the box, where Muto easily turned Young and buried Newcastle’s second.
Mourinho, who had joked with former Chelsea charge Kenedy in the tunnel and playfully squirted a water bottle at a television camera before kick-off, appeared far less jovial by then.
As he gesticulated wildly on the sideline, his players looked at each other in apparent shock.
Mourinho acted quickly in response, sacrificing Eric Bailly, a £30m specialist signing, after just 19 minutes. He installed Scott McTominay, a relatively inexperienced midfielder, in the centre of defence in order to make space for Mata.
That reflected a season of confusing decisions and a summer of transfer frustration during which Mourinho made no secret of his desire to sign another centre-back.
Manchester United certainly looked no more solid after the switch as Muto came close to a third and Mohamed Diame strode within striking range unchallenged.
The home side were on to their third defensive formation by the start of the second half as Fellaini replaced McTominay. With Mourinho’s half-time words apparently having the desired effect, they finally hit on a line-up that worked.
United were more purposeful and urgent, and chased down the game with a determination reminiscent of some of Sir Alex Ferguson’s finest days.
The glee on the final whistle should be tempered by the strength of the opposition, though.
Newcastle are without a win in their eight league games this season and, once Mata’s goal went in, lost belief and shape. Against tougher opponents, Manchester United may well have found such an escape impossible.
After meeting manager Rafael Benitez and some of the squad at an Italian restaurant on Wednesday in an apparent bridge-building exercise, Newcastle owner Mike Ashley was in attendance for his third match in a row.
The visitors are in dire need of his interest and, more importantly, his investment.
Two points from eight games represents the Magpies’ worst start to a top-flight season in the era of three points for a win.
With only goal difference keeping them from the bottom of the table, Benitez will surely lobby for more money to spend in January after failing to persuade Ashley to back his judgement in the summer.