Rocket Ronaldo launches United into Arsenal’s path

Sir Alex Ferguson was last night plotting how to beat his old adversary Arsène Wenger to a place in the Champions League final after his side rediscovered their defensive obduracy to prise out a win against the Portuguese champions.

An exquisite, dipping 40-yard effort from Cristiano Ronaldo saw United prevail in Porto despite a tense last half-hour of relentless pressure – but even greater obstacles are to come for Ferguson against Wenger, the man he described last week as his greatest challenger in the game, and whose side thumped Villarreal 3-0.

"Of course it's a different situation from normal situations we've had against Arsenal in recent years – a two-leg affair," Ferguson said. "Obviously I would be quite happy to win at Old Trafford 1-0 – that would be a perfect scoreline for me. Hopefully we can win the home leg and its something to build on. It won't be easy – a very difficult game."

But Wenger, who watched Theo Walcott score a goal to match Ronaldo's to set up last night's win at the Emirates, has precisely the same ambition for the semi-final first-leg at Old Trafford on Wednesday 29 May. "Always try and score in the first game," was the way Wenger put it. "Both teams like to go forward so it will be a promising semi-final, very interesting. It is difficult because of the quality of the teams. History always has a part to play but more important is the form on the day."

Wenger has the upper hand this season, after the scintillating 2-1 win over United last November which Ferguson was remembering last night. Now United's destiny is bound up tightly with Arsenal, a side they must play three times in the space of 18 days including a vital Old Trafford league clash.

Ferguson acknowledged the importance of the returning Rio Ferdinand, who, he said, had steadied the defence. But the United manager's decision to post Ronaldo into a centre-forward's role, from which he caused trouble for Porto's centre-backs early on, was also critical to United becoming the first British team in 42 years to beat Porto on their own soil.

"He is the quickest player we have," Ferguson said of Ronaldo, who had scored only one Champions League goal before last night. "I felt that by using him in that role we could stretch their centre-backs anyway. The goal was obviously sensational but he's always a threat." Ronaldo said: "The last five games we did not play great and we hope this [win] will change that."

Arsenal displayed more of their strong recent form by building on their 1-1 first-leg draw. "I said we would play to win and you could see that from the team we had out," Wenger said. "We have confidence. That is down to the slow progress we have accumulated from game to game in the championship. Confidence transfers from one competition to another." Theo Walcott scored the first goal, collecting a Cesc Fabregas flick before running clear and chipping in. Emmanuel Adebayor put the hosts firmly in charge, producing a neat finish with the outside of his right foot. Sebastian Eguren was then sent off for disputing an Arsenal penalty that Robin van Persie scored.