Mark Viduka blew the title race wide open at Old Trafford last night, when the Australian striker scored a headed equaliser which could see Manchester United’s lead at the top of the table reduced to a single point if Chelsea win at Newcastle today.

United were leading through Kieran Richardson’s first league goal this season and apparently cruising to another routine victory when, as the first half went into stoppage time, Viduka nodded home Stewart Downing’s cross at close range.

As significant as the result is the loss of yet another defender, Rio Ferdinand, with a recurrence of his groin injury. Already without Nemanja Vidic, Gary Neville and Patrice Evra, United will have to field a patched up defence, without a single first choice in any of the the four positions, when they play Milan in the first leg of their Champions League semi-final at Old Trafford on Tuesday night.

How many of them will recover in time for the resumption of the Premiership race at Everton next Saturday is anybody’s guess, but the prognosis is not encouraging. Sir Alex Ferguson was not about to admit as much, but he must be kicking himself for not substituting Ferdinand as soon as he went lame, near the end of the first half.

Instead, the manager kept his key defender on the field until half-time, and looked on, aghast, as Viduka ran past Ferdinand, then darted ahead of Wes Brown at the near post to head home. Another day, another crunch game in what has become an enthralling title race. Chelsea, playing this afternoon, could only sit back with fingers crossed as United again sought to open up a six-point gap. Jose Mourinho and company will have been cursing after precisely two minutes and 57 seconds, when a long ball delivered from his own half, caught Boro square and Rooney ran on and rounded Mark Schwarzer, then left it to Richardson to tap the ball home.

Boro appealed for offside, in vain. It was their defenders, not the officials, who were culpable. For the Teesside contingent, the omens were ominous. Ferguson admitted his team would need “an immense amount of luck” to pull off a second treble, and said that given a choice of the three trophies, his preference would be the league title.

With that priority in mind the United manager, unlike Liverpool’s Rafael Benitez, did not rest half his team before the Champions League semi-finals in midweek. The only notable absentee from the starting lineup was Ryan Giggs, and he was on the bench, and called on in extremis for the second half. Much had been made beforehand of the problems Boro have with Ronaldo — “paranoia” was the word Ferguson used. Gareth Southgate is by no means alone in believing the Portuguese trickster takes a tumble a mite too easily, but what a player. The world’s best? Pele has expressed doubts, and my vote for Footballer of the Year goes to the one-man strikeforce and set piece defender par excellence called Didier Drogba, but Ronaldo on his day is worth all that inflated admission money, and more.

One dexterous feint and sleight of foot midway through the first half bemused two opponents and had the crowd purring. Southgate and his players had nothing but his genius to complain about here, as Portugal’s finest retained his equilibrium while strutting his stuff. There was an air of inevitability about the incident when George Boateng, who had warned Ronaldo not to try to “take the micky”, was booked after 35 minutes, his tormentor’s mesmeric feet luring him into a clumsy, rather than malicious, foul.

The referee, Peter Walton, was right to produce the yellow card on that occasion, but wrong for booking Paul Scholes when Fabio Rochemback conned him with an obvious dive, and again when he took Ole Gunnar Solskjaer’s name for a legitimate challenge on Schwarzer. A rare break out by Boro, with Yakubu at the forefront, was snuffed out by a well-timed tackle from Brown on the 18-yard line, and Edwin Van der Sar was called upon to punch clear the occasional corner, but United, as is their wont in such company, played nearly all the cohesive football. They were in control and cruising when the equaliser hit them out of nothing as the first half went into stoppage time. Ferdinand was lame, and little more than a spectator when Boro worked Downing into a crossing position on the left. The England winger’s delivery was good — something that cannot be said often enough when he is on international duty — and Viduka darted in ahead of Brown at the near post to score a classical centre-forward’s header from five yards.

Ferguson, visibly agitated when he reappeared from the dressing room for the second half, sent on Fletcher and Giggs and signalled urgently to the crowd to raise the volume and lift their nonplussed team. The reorganisation necessitated by Ferdinand’s departure saw Fletcher take over at right-back in place of O’Shea, who moved into the centre of the defence to partner Brown. Giggs took up his customary station, on the left of midfield.

While the redeployment was still taking shape, Boro threatened to take the lead. Andrew Taylor’s short, lofted pass left Viduka one-on-one with Van der Sar, but this time the goalkeeper stood tall and made a vital save. So assured for 99 per cent of the first half, United were consumed by nerves throughout the second, with Ferguson in Mr Angry mode.

It really is, as he likes to call it, “Squeaky Bum time.” Over to you, Chelsea. You have your chance up at Newcastle today.