Manchester - Arsenal manager Arsene Wenger said that Danny Welbeck had been motivated by a desire to prove Manchester United wrong after he knocked his former club out of the FA Cup.
A Manchester-born United academy graduate, England striker Welbeck left for Arsenal in a $24.2 million deal last September after falling out of favour under new manager Louis van Gaal.
The Dutchman claimed Welbeck was not good enough to hold down a starting place at Old Trafford, but his words returned to haunt him as the 24-year-old earned holders Arsenal a 2-1 win on Monday that set up a semi-final meeting with either Reading or Bradford City.
"We want all to do well when we play against our former club to show that we are a great player, but it's not easy to deal with the mental situation of it," said Wenger, whose side had not won at United since September 2006.
"But he focused just on his game and didn't do anything special, just played football like you want him to play. I think he has shown mental strength, because it's not always easy to deal with that."
Wenger added: "He wants to win. He is a team player. What I like with Danny is he's intelligent, he wants to do well for the team, he's a great talent and recently has done extremely well for the national team."
Welbeck was moved on at United partly to accommodate Radamel Falcao, who signed from Monaco on an initial loan deal.
The Colombian star has failed to impress in Manchester, scoring only four goals in 20 appearances, and Van Gaal offered an unconvincing justification of his motives for bringing him in at Welbeck's expense.
When it was put to him that Falcao was struggling, he told a journalist: "He has scored four goals and has three or four assists, so that is his contribution. He stimulates also the other players, so that is an aspect of the profession.
"But it is now easy for you to say that. You are very happy to say that. I see that in your face."