"The conditions made things a bit difficult in terms of the ball coming off the surface quickly, but I think we controlled that part well," the United boss told MUTV after the 1-0 win.
"We played with good patience and good speed and stretched them really well.
"QPR haven't lost a lot of goals recently and they defended very well as we expected. So it was always going to be tough.
"But overall I'm very pleased by the attitude of the players. They worked very hard and we're all delighted to get through.
"We're used to teams coming here and defending. But what we did well was making sure we had them on the edge of their box for most of the game.
"It was just a matter of opening up and getting the first chance, which proved difficult to begin with."