Ole Gunnar Solskjaer knows all about the importance of using your substitutes and so it proved as Romelu Lukaku came off the bench to help earn Manchester United a fourth victory in the first four league matches under him.
In fact, only one other United manager has achieved that feat in the club's illustrious history - Sir Matt Busby, no less, in 1946 - which is some achievement by Solskjaer considering the confidence-shredded desperation he inherited at Old Trafford.
The club's former super-sub striker, who of course made such a happy habit of scoring when he came on, will regard this as the hardest-earned of his four wins and it is all the more important because of that.
Lukaku was only on the pitch for 40 seconds before he scored with his first touch, before Marcus Rashford added a second, and this result also came with a first clean sheet for Solskjaer even if they did give up chances and will have to play far better than this against better opponents.
Importantly for United, it closed the gap to fourth-placed Chelsea to six points in that vital race for a Champions League place. For Newcastle, it means it is just one win in seven and they are in danger of getting sucked down into the relegation dogfight.
Despite Newcastle's troubles, despite their uninspiring form, it felt like more of a test for Solskjaer than his three previous games. Not least because Rafa Benitez would relish the challenge of blunting the caretaker's sharp, free-flowing start at United.
Benitez also sensed a vulnerability in United's orders to play the ball out from defence with Phil Jones, replacing the suspended Eric Bailly, one of three changes, clearly being targeted. Twice Jones erred. There was a weak header and then he dallied in possession before recovering well to challenge Salomon Rondon as he shaped to shoot inside the penalty area.
The pace of Christian Atsu was also a problem for the visitors; as was the space he was afforded. Twice he forced saves - comfortable enough, in truth - by David De Gea before he sprinted through on the left and dragged a shot across goal after being picked out by Ayoze Perez.
United lacked security as they pushed on and Newcastle preyed on it and even showed a bit of flair of their own: the biggest early cheer came when Atsu "nutmegged" Paul Pogba. But would they rue those missed chances?
For United, Marcus Rashford carried their greatest threat and having already forced Martin Dubravka to push out a near post free-kick the goalkeeper had to react quickly to deny the striker after Fabian Schaar missed a simple long ball forward. Soon after and Anthony Martial miscued a half-volley onto the roof of the net before Pogba also failed to make sufficient contact after he was teed up on the area's edge.
More of a pattern was set. Newcastle kept their shape, defended strongly, led by Jamaal Lascelles, but were indebted to Dubravka once again as he reacted quickly to deny Juan Mata with his legs as he threatened to run onto a loose ball inside the area and round the goalkeeper.
But no goal. It meant that, for the first time under Solskjaer, United had not taken a first-half advantage with them into the break. Not that they deserved to. Newcastle had had opportunities even if United had claimed more than 70 per cent possession.
It remained tight; cagey and predictably so. As Martial tried to pick out a team-mate with a cross there were nine Newcastle players waiting inside their own area while play was also broken up by a series of injuries and hold-ups.
What would the response be?
Victor Lindelof held off Rondon and charged forward to find Rashford who cut back inside but shot so wildly the ball went out for a throw-in.
On the touchline Solskjaer clapped enthusiastically, hailing the urgency and intent.
As strongly as they defended, blocking out Shaw and Rashford, Newcastle still carried a threat of their own and once again Atsu found the space.
This time he crossed low with the ball just running ahead of Rondon. Soon after and Shaw slid in to stop a Perez shot with Newcastle unsuccessfully calling for a penalty as Lindelof barged Atsu.
The frustration grew for United with Matt Ritchie shouldering Rashford out off his stride as he attempted to reach a threaded pass.
Solskjaer had seen enough and made a double change. Lukaku and the - surprisingly - fit-again Alexis Sanchez came on. It worked. Rashford fired in a free-kick and although the ball moved Dubravka had to hold on to the shot but spilt with Lukaku charging in to side-foot home the rebound. It was his first touch.
Benitez will surely reflect on why his team only mounted a two-man defensive wall.
Yet another chance fell to Atsu but although he forced De Gea into a dive, the ball flew wide.
As Newcastle pushed they lost the ball with United breaking quickly through Lukaku and Rashford with Sanchez also joining in. He pushed the ball through to Rashford who had drifted free and calmly side-footed the ball past Dubravka to settle it.
© Daily Telegraph, London