On his first return to Old Trafford, Danny Welbeck dumped former club Manchester United out of the FA Cup and sent current employers and holders Arsenal onto a semifinal meeting with either Reading or Bradford City.

The Manchester-born forward, deemed surplus to requirements by Louis van Gaal last summer, celebrated with unmuted joy at the stadium he long called home after capitalizing on a woeful back-pass from Antonio Valencia to put Arsenal 2-1 to the good with half-an-hour remaining. Adding salt to United wounds and dramatically limiting their chances of hauling the visitors back for a second time, record signing Angel di Maria was shown two yellow cards in quick succession for diving and then attempting to grab referee Michael Oliver.

The drama was in keeping with an always engaging contest, in which the vulnerabilities of both teams contributed at least as much to its entertainment as the quality on show. The two most successful clubs in the competition’s history had quickly exchanged goals in the opening half, with the defensive acumen of both severely lacking. Nacho Monreal was the unlikely scorer of the opener before United captain Wayne Rooney responded with a flying header. But it was Valencia’s hideous error and Welbeck’s pace and anticipation that proved decisive in handing Arsenal a first win at Old Trafford since 2006 and keeping them very much on track to retain the trophy they hoisted aloft last May.

Given they’ll take on side from a least a division below in the last four, their chances look good of at least making another final. Ultimately their progress past a Manchester United team that they had beaten just once in their last 15 meetings was well deserved. Arsene Wenger’s men showed the greater solidity as the match progressed and would have won by more had it not been for further brilliance with the gloves from David de Gea.

But both teams were afforded ample openings early on. In the opening half it was Manchester United’s right flank, Arsenal’s left, that proved the key area of the pitch. United were targeting it going forward in getting Di Maria cutting inside and finding Marouane Fellaini peeling off to the back post to use his considerable size advantage against young Arsenal right-back Hector Bellerin. Clearly a threat with his size, it was the Belgian’s lack of dexterity with his feet on more than one occasion meant he failed to take advantage of the space he helped create in the box.

With United were enjoying the majority of possession and Di Maria was having an impact going forward, his failure to track back frequently caused problems as Arsenal looked to spring forward on the counter attack. It was no surprise when it proved the avenue for the opening goal 25 minutes in. In truth the gaps in United’s defense weren’t limited to their right side, with Alex Oxlade-Chamberlain able to wriggle past several challenges on the edge of the box, including the dragged across right-back Valencia. When the Arsenal midfielder slid the ball across the area, Di Maria was caught dozing and Monreal left free to beat De Gea with an assured side-foot finish.

But just three minutes later, with the sizable Arsenal contingent inside Old Trafford still celebrating, United pulled level when their record signing showed his quality at the other end. The former Real Madrid star’s cross exposed a huge gap between Arsenal’s center-backs, Laurent Koscielny and Per Mertesacker, and Rooney stooped to head past Wojciech Szczesny and continue his fine scoring record against Arsenal.

United made two changes at the interval, with Phil Jones replacing Luke Shaw at the back and the arrival of Michael Carrick in place of Ander Herrera surely designed to give them more solidity in the middle. But Arsenal gained more presence centrally, too, when Aaron Ramsey was brought on early in the second half for the injured Oxlade-Chamberlain.

And Arsenal were more assured and disciplined after the interval, limiting the effectiveness of a United team whose main weapon worryingly remains the physicality of Fellaini. At the back errors continue to blight their play, with Valencia’s scuffed back pass one of the most egregious seen all season. Welbeck’s quality of finishing was seen as the primary reason for his exit to Arsenal last summer, but he couldn’t miss after touching past De Gea.

United never looked like recovering the deficit, especially after Di Maria brought further scrutiny to what continues to be a disappointing first season at Old Trafford. After flinging himself to the ground and being cautioned, the incensed Argentinean tried to haul Oliver back to remonstrate further. The contact with the official was minimal, but there could be no complaints when he was shown a second yellow and directed toward the tunnel.

Adnan Januzaj was booked, too, for a theatrical fall to the turf, and United were left grateful that the ability of De Gea to fling himself around his goalmouth stopped the final score from being more convincing. For Manchester United, it is now Champions League or bust in Van Gaal’s first season in charge.