O'Shea is United's unlikely saviour

Arsene Wenger's face told the story. The smile playing across it late last night was not that of a losing manager and it said that he knew he should have been out of the door of this tie and down the road, not still hammering away at it. His opposite number had declared, minutes after dispensing with Porto in the Champions League quarter-final, that he would "settle for 1-0 at home" to Arsenal in the semi-final first leg, but that was then. Here and now was a glorious opportunity spurned.

For 45 minutes, Sir Alex Ferguson's team actually lived up to their manager's billing, playing breathtaking football, Manchester United football, stuff of such absolute supremacy that you felt Arsenal were on their way to something resembling the 6-1 defeat, eight years ago, or the 4-0 FA Cup defeat last season. For a second successive night, a wall of yellow was out there attempting to hold back the tide, but this one was not Chelsea's. It was besieged and porous and if one moment distilled all the pre-eminence it was Wayne Rooney, bringing an innocuous ball under control 40 yards or more out on the left, glancing up, and thumping it towards Manuel Almunia's goal. The advertising hoardings took it, but Rooney had made a point.

It was one reinforced when John O'Shea struck an exquisite effort to convert Michael Carrick's low cross from the right of the box. The acres of space in which Kieran Gibbs left O'Shea underlined that the four goals Liverpool scored against Arsenal last week were no fluke. Wenger's side might have gone 20 league games without defeat, but without William Gallas and Gaël Clichy their defence is a liability. This, plus the absence of an Arsenal away goal, will give Ferguson much hope.

The man who hammered at that defence most was Carlos Tevez, selected ahead of Dimitar Berbatov in an indication that it was energy Ferguson sought. He picked up from where he had left Tottenham on Saturday – on their knees – buzzing like a bluebottle and denying Arsenal the chance so much as to pass the ball out of defence. Cesc Fabregas might have created something in the first half-hour if he had received more than a couple of passes. Samir Nasri did not, to all intents and purposes, exist.

But a failure to convert chances has been a recurring theme of this season. Ferguson has remonstrated with his players about it and there is no serial offender quite like Cristiano Ronaldo, who has the unenviable position at the top of the Champions League "shots off target" chart. It was his and United's misfortune to find Almunia in the kind of form which can win tournaments, but Gibbs had still left Ronaldo with enough time, when taking down a Rooney cross two minutes into this match, to control with a knee and foot before blasting across the six-yard box.

Almunia played a mighty part, though. It was not just his reactions – the sharpest of low, left-hand saves from Tevez, a superb save from Rooney, a header from Ronaldo clawed away – as his tactical awareness and positioning which marked out this performance. His six first-half saves, in a first half-hour where United took 65 per cent of possession, have left Ferguson with only a marginal advantage at the Emirates.

It is a margin further reduced by that familiar foe of his: fixture congestion. There is another Saturday lunchtime kick-off looming and, though Ferguson's side for the visit to Middlesbrough will resemble his FA Cup semi-final team, he needed little reminding last night that the semi-final home draw against Milan two years back was followed by Saturday lunchtime football and annihilation in San Siro. Added to that is the worry that Rio Ferdinand, who was in hospital last night for X-rays on a cracked rib, might be missing for next Tuesday's return.

Such worries should never have featured in Ferguson's conversation. "Believe" read one of the mosaics United's fans held up before kick-off and their side, with a volume of support not heard here since last season's semi-final home leg against Barcelona, certainly did. The Arsenal right flank did, after all, prove to be the decisive area of play, but not in the area of turf where Theo Walcott was running at Patrice Evra. It was another French defender, Bacary Sagna, standing 20 yards behind Walcott, who was besieged, Wayne Rooney thundering at him again and again.

The warning signs took only two minutes to appear, with Rooney rising above Sagna to meet Darren Fletcher's cross, forcing Almunia to claw the ball away. Rooney is United's catalyst, imbued with energy which was too much for either Mikaël Silvestre or Kolo Touré. The spirit telegraphed through to midfield too, Anderson's first half providing some of his best football in a generally unconvincing season and Carrick showing a willingness to be in the opposition defence.

There were fleeting threats from Walcott. Heturned effortlessly away from Evra and sent in a ball from which Emmanuel Adebayor teed up a shot for Fabregas – Arsenal's first on target, after 27 minutes. Given more supply he looks like he could do some damage in north London, but it was United's tendency to let the pace drop which allowed Arsenal back in. One minute Fletcher was dispossessed by Fabregas, who exchanged passes with Adebayor and ran into the box for Rio Ferdinand to make a wonderfully timed tackle. The next, both Nemanja Vidic and Ferdinand were screaming at Anderson for more commitment after first Nasri, then Fabregas had been allowed to run through United's midfield. When Adebayor was allowed to turn and fire narrowly over, the threat of the away goal which Ferguson had feared was quite clear.

Ronaldo attempted to make amends for earlier misdemeanours, when he took a ball from Giggs and strode towards the Arsenal goal before clanging a 35-yard shot against the Arsenal crossbar. But there were threats at both ends by then. Nicklas Bendtner, on for Walcott, thundered a header wide after meeting a Fabregas free kick. Cue a collective sigh of relief. United are ahead – but only just.

Manchester United (4-3-3): Van der Sar; O'Shea, Ferdinand (Evans, 87), Vidic, Evra; Fletcher, Carrick, Anderson (Giggs, 66); Ronaldo, Tevez (Berbatov, 66), Rooney. Substitutes not used: Foster (gk), Park, Scholes, Rafael.

Arsenal (4-2-3-1): Almunia; Sagna, Touré, Silvestre, Gibbs; Diaby, Song; Walcott (Bendtner, 70), Fabregas, Nasri; Adebayor (Eduardo, 83). Substitutes not used: Fabianski, Denilson, Ramsey, Djourou, Eboué.

Referee: C Bo Larsen (Denmark).

Att: 74,733

Manuel's magic: Key first-half saves

2 min Wayne Rooney's downwards header skids off Bacary Sagna's head and is goalbound until Almunia scampers across his line, dives and flicks it clear.

17 Almunia gets down low to make an excellent save from Carlos Tevez from six yards, then manages to block the rebound.

29 Almunia chases across his goal-line to save a point-blank header by Cristiano Ronaldo from three yards after Tevez curled in a wonderful cross from the inside-right flank.

Man-for-man marking

Manchester United

Edwin van der Sar

Quiet evening for a Champions League semi-final. Scarcely a shot to save 6/10

John O'Shea

A rare goal, well taken, and plenty of opportunities to attack down the right 7

Rio Ferdinand

Largely untroubled night, as cool and composed as ever when necessary 7

Nemanja Vidic

Like his partner, kept Adebayor quiet and had little else to worry him 7

Patrice Evra

Tormented recently by Aaron Lennon but handled Walcott well and went forward, too 7

Darren Fletcher

A long way from being the most popular United player but workmanlike 6

Michael Carrick

Back to his best with some imaginative passing and neatly set up O'Shea's goal 8

Anderson

Much more vigour than his opponents in midfield. But still no United goals in 72 games 6

Cristiano Ronaldo

Did not take enough advantage of Gibbs' inexperience. Hit the bar 7

Carlos Tevez

Committed and dangerous down the middle, thoroughly justified his start 7

Wayne Rooney

Out on the left in first half then the right – and impressive all round 8

Substitutes

Ryan Giggs (Anderson, 66) 7; Berbatov (Tevez, 66) 6; Jonny Evans (Ferdinand, 87) n/a

Arsenal

Manuel Almunia

Even better than Petr Cech on Tuesday; seven good saves in the first half-hour alone 8/10

Bacary Sagna

Found Rooney a handful. Not able to offer Walcott much support up the wing 5

Kolo Toure

Some unusually poor positioning offered United chances through the middle 5

Mikael Silvestre

Unlucky deflection for the goal marred solid performance against his former club 7

Kieran Gibbs

Tough stuff for the teenager up against Ronaldo, Rooney, or O'Shea but kept going 7

Theo Walcott

A good duel with Evra when he was given the ball, but needed better service 6

Alex Song

Unable to make much of crucial role in midfield where he and Nasri were outplayed 5

Samir Nasri

Saw off United in November but Arsenal needed more from him in central midfield 5

Abou Diaby

Stayed out on the left without helping either to subdue Ronaldo or create anything 5

Cesc Fabregas

Worked hard whether in his forward role or deeper but could not open up defence 6

Emmanuel Adebayor

Like many a lone striker of an away side, suffered from not seeing enough of the ball 6

Substitutes

Nicklas Bendtner (Walcott, 70) 6; Eduardo da Silva (Adebayor, 83) n/a

Steve Tongue