Discarded by United manager Louis van Gaal last summer the only Mancunian on the pitch last night knocked his old club out of the FA Cup with the winning goal at Old Trafford.
Van Gaal deemed Welbeck surplus to requirements and instead elected to invest in expensive signings such as Ramadel Falcao and Angel Di Maria, both of whom have yet to really ignite their careers with the Red Devils.
The £16m (€20m) he was sold for must feel like a pittance to United fans this morning.
It’s hardly been a bed of roses for Welbeck at Arsenal mind, but his eighth goal of the season is still double what Falcao has managed during his spell at Old Trafford.
Welbeck’s winner, after Wayne Rooney had cancelled out Nacho Monreal’s opening goal, must have been a bittersweet moment for the 24-year-old who had been at United from the age of eight until last summer.
It also ensured the Dutchman’s first season in charge will end without a trophy.
In contrast, it was a night to savour for Arsene Wenger.
The Arsenal boss was quick to hail Welbeck.
“Danny Welbeck has pace and a little bit of psychological consideration. We knew we would have counter attacking chances, and he was ideal for that.
“You want to do well when you play against your former club. He focused just on his game, and he showed mental strength because it’s not always easy to deal with that. I knew very late he would play.
“Did he have extra motivation? I just think he wants to win, do well for team. He is a great future and great talent.”
This was a ferociously competitive game.
With neither club challenging for the title, and Arsenal seemingly on their way out of the Champions League, both clubs needed something to spice up a season where finishing third is the realistic height of their ambition.
Maybe the quality was not there at times, but this had the hallmarks of a heavyweight clash of old.
After a frantic start the game exploded into life just before the half-hour mark.
Alex Oxlade-Chamberlain’s tricky feet mesmerised the United defence as he twisted this way towards the edge of the penalty area.
Antonio Valenica was also drawn into the trance which allowed Monreal’s overlapping run to go unchecked and the Spaniard kept his composure to strike the ball past David De Gea at his near post.
The visiting 9,000 fans were jubilant, but United’s reply was instant as they also capitalised on some equally poor defending.
On the right flank Di Maria cut back inside on to his left foot and picked out Rooney, who was remarkably allowed the freedom of the penalty area by both Laurent Koscielny and Per Mertesacker, and he powerfully headed in.
It was Rooney’s fourth goal in five games since he returned to a more familiar central striking role.
Wenger came off his line to vent his fury at referee Michael Oliver when Welbeck, whose pace regularly stretched United’s defence, went to ground after his right shoulder was grabbed by Marcos Rojo. Arsenal’s appeals were ignored.
It was breathless stuff; Di Maria forced Wojciech Szczesny to save at his near post, Alexis Sanchez curled over the crossbar while Marouane Fellaini shot straight at the Arsenal keeper from a good position.
Perhaps the FA Cup’s two most successful teams — with 11 victories apiece — were always going to be produce a game of such intensity and there was no let up after the interval.
Di Maria’s angled shot flashed past the post on the hour-mark before Arsenal regained the lead after they capitalised on a defensive blunder.
Valencia received the ball from Phil Jones and the Ecuadorian’s weak pass back was seized upon by the alert Welbeck, who beat De Gea to the ball and calmly slotted into an empty net.
Despite the modern trend Welbeck celebrated, and did so respectfully. The visiting Arsenal fans delirious by comparison.
United tried to rally and Chris Smalling should have equalised when he blazed over from a corner after Michael Carrick’s neat flick while Fellaini headed straight at Szczesny.
With 15 minutes left Santi Cazorla thought he had put the tie beyond United with a delicious volley for De Gea to scramble across his goal and tip the ball past the post.
United’s task in the remainder of the game was made more difficult when Di Maria, arguably their best player, was bizarrely sent off.
The winger was initially booked for diving under minimal contact by Aaron Ramsey, and then shown a second yellow after he grabbed referee Oliver’s shirt.
But despite five minutes of added time there was no way back for United.
MANCHESTER UNITED (4-2-3-1): De Gea 5; Valencia 4, Smalling 5, Rojo 6 (Januzaj 73; 6), Shaw 5 (Jones 45; 6); Blind 6, Herrera 5 (Carrick 45; 6); Di Maria 7, Fellaini 7, Young 6; Rooney 8
ARSENAL (4-2-3-1): Szczesny 5; Bellerin 5 (Chambers 66; 7), Mertesacker 6, Koscielny 5, Monreal 7; Coquelin 7, Cazorla 6; Oxlade-Chamberlain 7 (Ramsey 51; 6), Ozil 6, Alexis 7; Welbeck 7 (Giroud 74; 6).
Referee: Michael Oliver.