"I think he will figure in many games," said United manager Alex Ferguson after the friendly, part of a four-team tournament in Munich that also includes Bayern Munich and AC Milan.
"It was his first game. For his first game, we are very satisfied," he told reporters.
Valencia, who joined from Wigan Athletic as a replacement for Cristiano Ronaldo, scored United's second goal in the 42nd minute with a powerful shot that slipped under keeper Roberto Abbondanzieri after he had slipped past two defenders.
"He is a good athlete, has good power and running ability, as we saw today with the way he created a good goal," said Ferguson.
"Maybe it was a mistake by the goalkeeper, but he created the opportunity and opened up spaces for himself."
United play Bayern on Thursday after the Germans defeated AC Milan 4-1.
(Writing by Karolos Grohmann, Editing by Justin Palmer)