The striker scored the first of his two goals for Manchester United in the eighth minute from just inside the Hammers half.
"It's such a wonderful goal you've got to admire the finish," he told Sky Sports News. "But to get off to a start like that having won the last three at home didn't help. It was wonderful, you have to admire the talent. He didn't even look up.
"If you look again though it's probably a foul by Rooney. Rooney pushes James Tomkins and it's difficult for the referee to see it.
"He stops Tomkins heading the ball. The assistant referee should have seen it but there you go. We didn't get a couple today."