Di Maria red card adds to van Gaal's woes; Wenger praises Welbeck

‘I think he's touched the referee and that's forbidden in every country, so he has no excuses’

‘We didn't lose to them, we lost because of our own performance’

Another unconvincing display from Manchester United was compounded by a needless red card for Angel Di Maria on Monday as the Argentine added to manager Louis van Gaal's woes.

Welbeck sinks United as Arsenal reach FA Cup semis

With United trailing 2-1 to Arsenal in the FA Cup quarter-final, Di Maria was booked for diving and minutes later grabbed the shirt of referee Michael Oliver, giving the shocked official little choice but to send him off.

It ended United's hopes of hauling themselves back into the tie and marred what had started off as a bright performance by the man signed from Real Madrid for 60 million pounds ($90.65 million).

Van Gaal, who now has virtually no chance of marking his first season with a trophy, had little sympathy for Di Maria.

"In Spain he knows that he doesn't touch the referee, but that is also in his emotion," the Dutchman told the BBC.

"I've already spoken with him, he knows my opinion but also I have to see on the video.

"I think he's touched the referee and that's forbidden in every country, so he has no excuses."

When Wayne Rooney cancelled out Nacho Monreal's opener for the visitors before halftime with a flying header, United looked as though they might continue their quest for a first FA Cup since winning a joint record 11th in 2004.

But they faded after the break and now only have a desperate battle for a top-four Premier League finish to play for.

That it was Danny Welbeck, sold by Van Gaal last summer, who poached the winner after a dreadful mistake by Antonio Valencia only rubbed salt into the wound.

"We didn't lose to them, we lost because of our own performance, and that's very disappointing," Van Gaal said.

Wenger praise for Welbeck as he proves a point

Players are often reluctant to celebrate goals they score against a former club but Danny Welbeck clearly enjoyed netting Arsenal's winner at Manchester United on Monday.

The England striker punished Antonio Valencia's shocking back pass just past the hour in the FA Cup quarter-final at Old Trafford to seal a 2-1 win for the Gunners.

Welbeck began his Arsenal career in style and a hat-trick in a Champions League game against Galatasaray in October looked set to light the blue touchpaper.

But the goals have dried up, partly because of injuries, and his winner against United was only his fourth goal for the club since he destroyed the Turkish side.

Arsenal manager Arsene Wenger selected Welbeck ahead of Olivier Giroud for the trip to United and his faith was repaid as the 16 million pounds ($24.17 million) signing put Arsenal into the last four where they will face either Reading or Bradford City.

"We want all to do well when we play against our former club to show we are great players but it is not easy to deal with the mental aspect of it," Wenger said.

"He focused just on his game and played football the way he wanted to. He has showed mental strength.

"He wants to win, he is a team player. He is intelligent. He is a great talent and has done extremely well for the national team as well. He has produced a great performance, defensively and offensively."

Arsenal had not beaten United in any competition since May 2011 and had suffered two FA Cup defeats against their fellow 11-time winners since beating Alex Ferguson's side on penalties in the 2005 final in Cardiff.