Arsenal's problems were brought into brutally stark relief at Old Trafford as they suffered a disembowelling at the hands of Manchester United, with Wayne Rooney scoring a hat-trick in an 8-2 victory for Sir Alex Ferguson's side.

The result was the most desperate defeat Arsenal have suffered in the Premier League, with their previous worst a 6-1 loss at the same ground in February 2001. On that occasion, as on Sunday, the root cause of the collapse was a hopeless, makeshift defence, but the current malaise enveloping Arsenal threatens to be something altogether more serious.

Rooney ran riot with two direct free-kicks and a penalty, Ashley Young scored two brilliant curling efforts, Danny Welbeck, Nani and Park Ji-Sung added further goals and Arsenal's futile replies came from Theo Walcott and Robin van Persie.

The Arsenal captain had missed a penalty in the first half but United comprehensively dominated throughout and could have had more, with Rooney unlucky to hit the post in a quite wonderful performance from the England striker.

Carl Jenkinson was also dismissed - the third red card shown to Arsenal in three games - and the result puts United top on goal difference, leaving Arsenal in 17th with one point from three games after conceding eight goals in a league game for the first time since 1896.

Following confirmation that Bacary Sagna and Thomas Vermaelen would both be missing from a team already ravaged by injury and suspension, and that Francis Coquelin would be asked to anchor the midfield on his league debut, a certain 6-1 defeat sprang to mind.

As it transpired, such a scoreline would have been favourable. Arsenal appeared ill at ease from the start and were given a warning after six minutes when Welbeck sprinted away from Laurent Koscielny before firing back across goal and wide.

With United superior all over the pitch, Arsenal were somewhat fortunate to see Andrei Arshavin escape with only a yellow card for a late and high challenge on Phil Jones. When the Russian then clattered into a rash tackle on Young, it was a mystery how he remained on the pitch.

Arsenal's strained defence gave way after 22 minutes: Anderson lofted a pass over the top of the defence, and both Koscielny and Johan Djourou completely failed to deal with Welbeck. Either man could have headed clear but instead contrived to allow the forward to head home from close range, enraging Wojciech Szczesny.

Inside four minutes Arsenal had the chance to draw level when Jonny Evans was penalised for pulling Walcott's shirt in the box to concede a penalty, but the away side's misery continued when Robin van Persie's weak, low shot from 12 yards was palmed clear by De Gea, earning the young goalkeeper an enthusiastic embrace from grateful colleagues.

It was a brief glimmer of threat from the Gunners, however, and United soon resumed their siege. Just before the half hour mark, Young left his mark on Arsenal with a goal of stunning quality. Armand Traore headed clear and Young took possession of the ball some 30 yards from goal, jinking away from Coquelin and bending a sumptuous effort out of the reach of Szczesny and into the top corner.

De Gea then produced a double save to deny Arshavin and Van Persie in quick succession but United remained firmly in control, almost adding a third when Welbeck sent a diving header wide from Rooney's excellent cross.

Welbeck was forced off with a hamstring injury but United's momentum continued unabated and Rooney made it three with an expertly taken free-kick that flew into the top corner after Jenkinson had hauled down Young to earn a booking.

Three minutes into added time at the end of the opening period Arsenal gave themselves some hope when Tomas Rosicky sprung open the defence to find Walcott, but his low effort flew through the legs of a culpable De Gea.

Within three minutes of the restart Young forced Szczesny into a fine save at his near post after more abject defending from Arsenal, but the Gunners improved going forward and represented more of a threat as Van Persie saw a fierce volley saved by De Gea. Arshavin charged in behind the defence looking set to pull one back only to drag his shot wide of the near post.

Defensive concerns continued to abound though and only a weak finish from Cleverley prevented the midfielder from adding a fourth following a one-two with Javier Hernandez. Young was then denied by a fine save from Szczesny before Nani failed to stab the ball home after Young squared from the rebound.

Arsenal's flimsy backline were torn asunder once and for all when United scored three times in the space of six second-half minutes. Rooney started the collapse when scoring a second direct free-kick, the striker curling the ball into the top corner as Szcesny was rooted to the spot having already started to move in the wrong direction.

Within three minutes Rooney had opened up the Arsenal defence to set Nani free, who contemptuously chipped the ball over Szczesny to make it five. Rooney then struck the post with an outrageous chip of his own before Park came off the bench and added a sixth when receiving a pass back from Young and slotting the ball out of the reach of the Polish keeper.

Van Persie pulled a goal back to make it 6-2 when lashing home from close range but the misery continued for the Gunners. Rooney completed a hat-trick by converting from the penalty spot after Walcott had fouled Patrice Evra, while Young piled yet more misery on Wenger's team with another exquisite long-range curler that was almost as good as his superb first effort.

The final whistle could not come soon enough for the visitors. Though United were imperious, the real story was the shocking decline of Wenger's Arsenal.

The Gunners have three days remaining of the transfer window to try and arrest their alarming slide; quite how they will persuade world class players to join a team so clearly in crisis is another question entirely.

Predicted Lineups:
Manchester United Starting XI: David De Gea; Chris Smalling, Jonathan Evans, Phil Jones, Patrice Evra; Ashley Young, Tom Cleverly, Anderson, Nani; Danny Welbeck, Wayne Rooney.

Arsenal Starting XI: Wojciech Szczęsny; Carl Jenkinson, Thomas Vermaelen, Johan Djourou, Bacary Sagna; Alex Song, Tomas Rosicky, Aaron Ramsey; Theo Walcott, Robin Van Persie, Andrei Arshavin