Manchester United signalled their intention not to let anything as trivial as a mounting injury list derail their treble drive as they smashed four past Bolton for the second time this season.

Park Ji-Sung and Wayne Rooney both scored twice as Sir Alex Ferguson's men surged to a victory which leaves them requiring a maximum 18 points from their last eight games to end a four-year title drought.

Not for the first time this season, Cristiano Ronaldo was the star of the show, as Bolton found themselves totally incapable of stopping the brilliant winger.

Yet the victory came at a price for the hosts, who were already missing six senior men through injury and suspension, as skipper Gary Neville was forced off with what a serious-looking ankle injury.

After half an hour of the onslaught it would have been difficult to know who was sitting most uncomfortably, Sam Allardyce or Steve McClaren - who had taken the opportunity to survey the start of a crucial weekend for him in the Old Trafford directors' box.

The game was only 10 minutes old when the England coach's day took a serious downturn as Neville lay on the ground in agony after his left ankle crumpled under a challenge from Gary Speed.

Neville could put no weight on his leg as he was helped to the touchline and the word swiftly came out that he could not continue.

Already, the chances of the United skipper being fit for international duty in Israel next Saturday appear slim to non-existent so McClaren, who had spoken of the need for experience in Tel Aviv, may end up turning to 18-year-old rookie Micah Richards.

If there is any comfort for McClaren, it is that England are not facing Portugal next week because, with Ronaldo in this mood, they would be virtually unbeatable.

Having already suffered heavily at United's hands once this season, Allardyce was keen to avoid a repeat.

Yet, after Bolton had received a major let-off when Park skied over from three yards, the visitors were well and truly flattened by a big red steamroller driven mercilessly by Ronaldo.

The opener came from an innocuous beginning as Wayne Rooney won a header with Tal Ben Haim close to halfway.

Ronaldo was on to the loose ball in a flash, darted not just to the by-line but down it, then picked out Park with a fine cut-back which invited the South Korean's precise finish.

A capacity crowd was still catching its breath when United scored one of those breakaway goals which have been such a hallmark of their success down the years.

Breaking out of their own area as they half-cleared Ivan Campo's long throw, the Red Devils streamed forward.

In the end only Ronaldo and Rooney were required to make contributions as the pair exchanged passes twice in a run which took them 80 yards downfield before Rooney beat Jaaskelainen with an impudent chip to register the 50th goal of his United career.

For a while it seemed Bolton would be humiliated in a manner seldom seen since Allardyce took charge seven years ago.

It was almost as if the visitors were so fearful of Ronaldo they dare not go near him, offering the winger a suicidal amount of space to run into every time he got the ball.

Jaaskelainen was spooked enough by his presence to allow a relatively weak shot to slip from his grasp just before the half hour, the rebound rolling kindly for Park to tap home his second.

From that point on it was a damage limitation exercise for Bolton, with Ferguson feeling sufficiently comfortable about his side's position to remove Giggs and - to a standing ovation - Ronaldo from the fray long before the end.

Only Jaaskelainen's save prevented Ronaldo getting his own name on the scoresheet for the 18th time this season but the winger's exit at least allowed Alan Smith to experience Premiership combat for the first time since his suffered those horrific injuries at Liverpool in February last year.

He was soon celebrating too after setting Rooney free with a lobbed pass which allowed the United forward to outpace Ben Haim before belting an unstoppable volley past Jaaskelainen.

The goal involved precisely five touches from the moment the ball left the United area to it entering the Bolton net.

It took Rooney's tally for the season to 15, five of which have come against Allardyce's team, who bagged a late consolation when Gary Speed slotted home from the spot after Nemanja Vidic had harshly been ruled to have fouled Abdoulaye Faye.

Teams:

Man Utd Kuszczak, Neville (Brown 11), Ferdinand, Vidic,Heinze, Ronaldo (Smith 70), Carrick, O'Shea, Park, Rooney,Giggs (Richardson 56).

Subs Not Used: Heaton, Evra.

Booked: Richardson.

Goals: Park 14, Rooney 17, Park 25, Rooney 74.

Bolton Jaaskelainen, Hunt, Ben Haim, Faye, Gardner, Nolan,Campo (Thompson 78), Speed, Davies (Teymourian 52), Anelka,Pedersen (Diouf 28).

Subs Not Used: Walker, Giannakopoulos.

Booked: Campo, Gardner.

Goals: Speed 87 pen.

Att: 76,058

Ref: A Wiley (Staffordshire).