An intriguing strand of Louis van Gaal’s opening Manchester United campaign is how the manager is rejuvenating Old Trafford careers. At the head of this list is Ashley Young, who entered this 169th derby as a footballer reborn and who was keeping £59.7m of prime football talent on the bench.

When Ángel Di María signed last summer to herald United’s new galáctico era he hardly expected that come spring he would be demoted by a winger who had lost his fizz and become a peripheral figure. Yet as this match passed the hour mark, United still held a 2-1 lead courtesy of the Young show during the opening stages. The starting XI were the same who defeated – Tottenham Hotspur and Liverpool and would have remained in place for last weekend’s win over Aston Villa if Chris Smalling had not been ill. The defender returned, as Van Gaal sent out what is beginning to look like his preferred lineup for a third time in four games.

This meant Young was again preferred to Di María, a tribute to how the 29-year-old has taken his chance since the former Benfica and Real Madrid winger – the British record transfer – was suspended following a red card in the FA Cup defeat to Arsenal.

The Argentinian may have to look elsewhere for his route back into the team after a Young contribution that featured his equaliser, the creation of the Marouane Fellaini goal that gave United the lead, and the ball to Smalling that confirmed a 4-2 victory.

In the 13 minutes between Young’s goal and the Belgian’s header, the winger turned the contest on its head. Until then Manchester City were the ascendant force, punching holes in a strangely overawed United at will.

If the champions were intent in proving tales of their demise are being greatly exaggerated the move that led to their opener after eight minutes was a fine start, Sergio Agüero scoring a sixth league goal in this fixture, and his first since 24 February.

The early lead was deserved. United were playing their worst for more than a month, when a 1-0 victory was earned at Newcastle United by an 89th-minute goal from Young, his only one of the campaign until this game.

As the blue wave continued, United appeared a side who might be engulfed. But instead of crumpling Van Gaal’s team showed the belief and impressive play that first clicked into place during those wins over Spurs and Liverpool.

Young’s finish was a scrambled effort from close in that showed his hunger. The cross with which he found Fellaini’s head for the second goal was illustrative of his quality.

Fellaini is another player enjoying a resurgence under Van Gaal. This was his sixth of the season for the club, the second in four matches. The Belgian has become a key Van Gaal lieutenant for the balance – as well as obvious ability – he gives the team.

Next up in the roll call of the comeback kids was Juan Mata, the £37.1m signing who had also found himself out of favour. Yet when Wayne Rooney slipped the playmaker in on 67 minutes Mata strode forward with the confidence of a player who scored each of their goals in the win at Anfield to beat Joe Hart and make it 3-1. This was Mata’s ninth of the season, already a productive return as the Van Gaal blueprint continues to appear ever more impressive.

So, too, does Young. A memorable outing that had begun when registering the first United goal ended with a pivotal role in the last, as he pinged in the free‑kick from which Smalling headed beyond a helpless Hart.

This fixture had been expected to reveal the state of health of both clubs. At the close the verdict was that despite Agüero’s late second goal, City are in some disarray. United continue to gaze upwards – with Young at the forefront.