SIR Alex Ferguson is backing Antonio Valencia to become the latest jewel in his Old Trafford crown after the £16m winger's dream debut for United. The Ecuador international scored what proved to be the decisive goal in a 2-1 win against Boca Juniors last night to make an immediate impact with the Premier League champions. And Fergie is convinced there is plenty more to come from former Wigan star Valencia, who will be asked to fill Cristiano Ronaldo's boots. The United manager said: "We are very satisfied with him. It was his first game because he had to go back to Ecuador for his work permit. "He has missed the pre-season work so far, but has shown he's got a good talent, nice balance and is a good athlete. There is something to work on there." While Ferguson beamed about Valencia, he was less than impressed with United's performance as a whole, despite them continuing their 100 percent record in pre-season and reaching tonight's final of the Audi Cup against Bayern Munich. "We were poor," he said. "It was a disappointing performance. The increase in pressure they put on the ball was something we were not used to after Far East. That was a real game and we are back in the real world. Hopefully we'll come on from that." Ferguson was at least pleased to see Anderson get on the score sheet with a stunning free-kick after failing to hit the back of the net in 76 appearances for United. "Maybe that will spark the boy off," said Ferguson. The worrying news for United was a thigh strain for Wes Brown, which saw the England international leave the pitch after just 37 minutes, while Nemanja Vidic pulled his calf in the warm-up. What is your verdict on Valencia's debut? Have your say.