Louis van Gaal
Louis van Gaal has hailed his team after they defeated Preston and confirmed Van Persie's availability for Swansea clash  Getty Images

Manchester United manager Louis van Gaal has praised his team's "unbelievable spirit" following their come-from-behind 3-1 win over Preston North End to book a place in the quarter-finals of the FA Cup.

After a goalless first-half, United went behind just two minutes into the second half, but goals from Ander Herrera, Marouane Fellaini and Wayne Rooney ensured the Red Devils did not become yet another casualty in the cup competition this year.

Despite not hitting the target in the opening 45 minutes, the manager was satisfied with his team's performance, who have been drawn against Arsenal in the quarter-finals.

But he was visibly impressed at the team's response after going a goal down, and believes that a change of shape in the second-half was key to their victory.

"I was reasonably satisfied. We didn't give anything away. The fights between Kevin Davies and the defenders were difficult but we didn't give anything away. The Preston goal was a little bit unlucky, it was deviated," Van Gaal said, as quoted by the Mirror.

"But then we showed an unbelievable team spirit. We changed the shape and that was the solution. We scored fantastic goals, a little bit lucky also I think. I liked the second goal a lot, we have trained that a lot," the Dutchman added.

There was more good news for United after the game as the former Bayern Munich manager revealed that striker Robin van Persie, who missed the Preston game due to injury, is fit again and will be available for United's trip to South Wales to take on Swansea City.

"Yes, he [van Persie] shall be fit," the Dutch manager confirmed following the 3-1 win at Deepdale.

The former Arsenal striker's return to fitness and Daley Blind's recovery from a head injury leaves just Phil Jones and Michael Carrick as the two United players still on the treatment table.