MANCHESTER United's championship pretensions can be laid to rest here and now. For the second home game running, they left the field to spasmodic booings after drawing with Aston Villa the fifth league match in succession in which they have been pulled back after taking the lead. The result leaves them without a win since September. Those statistics tell their own story. The performance, in front of their second largest crowd of the season 44,804 tells an even harsher one. Against a very average Villa side, United were mediocre. The clubs' positions 12th and 13th before the start suggested a mid-table clash, and that was exactly what we had. An intermittently-exciting game but one far short of the sort of quality you expect from real championship contenders. To add to United's frustration, they lost Colin Gibson, who was stretchered off only 19 minutes into his first home match since a cartilage operation in the summer. Gibson collapsed clutching his knee after collecting a sweeping pass from Mark Hughes and hitting over a deep cross with no one anywhere near him. Gibson is the latest addition to a continual injury list with Paul McGrath and Norman Whiteside both long-term absentees, and Viv Anderson, Mike Duxbury and Billy Garton playing on while carrying minor injuries. Yet McGrath and especially Whiteside apart, it is hard to point at any of them as providing a real excuse for United's results and McGrath has been replaced at considerable expense by Mal Donaghy, who made a satisfactory home debut. But equally telling for United fans was that rather than the expensive new recruits Mark Hughes, Jim Leighton or Donaghy their star performer was Liam O'Brien, the 24-year old Dubliner whose chances at Old Trafford have been so restricted that he has begun only 16 first team games in his three years at the club and whose presence on the transfer list has so far provoked widespread disinterest. Whatever happened in the tunnel or indeed on the pitch, at Plough Lane last Wednesday, it seemed as if it has caused United to lose a little more of their zest for the game. In a lacklustre first-half. the exception was Irish international O'Brien who was apparently the only United player eager to test Nigel Spink's agility until Bruce came up to lend a hand. O'Brien began his assault on the Villa goal after only four minutes as Mountfield was adjudged to have handled the ball just outside the penalty area. The free-kick was tapped square to the powerful Dubliner who hit the bar. Two minutes later, he had another drive from closer in as Chris Price unnecessarily obstructed Hughes but again the Villa wall proved equal to the task. O'Brien's next attempt after the departure of Gibson was much closer as he received the ball from Brian McClair and fired in a hard low shot which took a deflection onto the post as Spink failed to reach it. Those were rare moments of excitement, a firework on the terracing pointing up the almost total absence of any on the pitch. Finally, however, after a clash of heads between Chris Price and Jesper Olsen brought the trainers on again, and as the first half dragged on interminably, United took the lead. It was a goal which Villa deserved to concede for their total inactivity even if United had done little to command it. Again. O'Brien was heavily involved, his low 30-yard shot forcing Spink to a diving save. From the resulting corner Bruce met Gordon Strachan's cross with an unstoppable header which bulleted into the roof of the net. That goal, or possibly their half-time talk, at last provoked Aston Villa into some sort of activity. Almost immediately. Tony Daley got away for a cross which forced Jim Leighton to his first serious save of the afternoon. That gave United a warning which they failed to heed and on the hour Villa broke away for the equaliser. David Platt sent Alan Mclnally speeding away down the right and he broke past Bruce to send a centre across the face of the goal to reach Gordon Cowans. Cowans swept it past Leighton for an equaliser which Villa hardly deserved and which once again sent a buzz of discontent through the home supporters.