Manchester United are in pole position to reach the Champions League final after beating Arsenal 1-0 at Old Trafford. A first-half goal by John O’Shea, on the eve of his 28th birthday, will give United a priceless advantage when the teams meet again for the second leg at the Emirates Stadium on Tuesday.

United will be delighted that they did not concede an away goal but Sir Alex Ferguson’s team would already have one foot in the final if they had pressed home their advantage in the first half. Cristiano Ronaldo hit the bar with a vicious long-range strike in the second half and only a series of smart saves by Manuel Almunia, the Arsenal goalkeeper, prevented United from extending their lead.

O’Shea’s goal, only his second of the season, came about after Arsenal failed to deal with a low cross from Michael Carrick. “The goal was a little early birthday present for me,” O’Shea said. “Their keeper made some great saves. We could have scored more but we are capable of scoring at the Emirates. Arsenal are a good team and they kept the ball well but overall we have to be happy.”

Arsenal have not conceded a goal in the Champions League at home this season, but they could have been out of the competition if they had not stepped up a gear after the interval. After a shaky start, Arsenal’s centre-back partnership of Mikael Silvestre and Kolo Toure grew in stature, but too many of their players – especially Cesc Fabregas and Emmanuel Adebayor – were out of sorts.

Arsenal’s best chance of the night fell to Nicklas Bendtner, who came on as a second-half substitute. The Denmark forward should have done better with a header when he beat Edwin van der Sar to a free kick from Fabregas.

“I believe it’s advantage to United,” Wenger said. “They played well and started strongly but we have a good chance to reverse it at home. We didn’t create enough but let’s not talk about what we didn’t do, let’s talk about what we want to do next week

“They could have scored a second and Almunia kept us in the tie. United played at a fast pace and closed us down well and we never got into our stride. We still believe we can do it at home and I still believe we can do it next week.”

Rio Ferdinand left Old Trafford in an ambulance after the game to have an X-ray on a rib injury and the United captain was replaced by Jonny Evans in the closing stages.

“I’m pleased with our performance level and maybe we should have scored four,” Ferguson said. “Before the game I wanted to win without losing a goal. The game’s not over because we can go there and score. This team can make chances again – maybe I’ll pick a different team with different tactics but we’ll have a goal threat. We reached a high level against a very good team. We know the tie’s not over, but we can score there.”