Rooney scored a hat-trick in an unbelievable performance at Old Trafford

Manchester United inflicted total humiliation on Arsenal and their embattled manager Arsene Wenger with a brutal victory at Old Trafford.

Sir Alex Ferguson's Premier League champions responded in spectacular fashion to Manchester City's outstanding 5-1 win at Spurs by returning to the top of the table with a result that represented Arsenal's worst defeat since 1896.

Wenger sent out a makeshift side depleted by injuries and suspensions - but even this cannot excuse the manner in which they were outclassed in all parts of the pitch and swept aside with such ease by United.

Wayne Rooney was United's inspiration with the sixth hat-trick of his Old Trafford career, but Ashley Young also made his mark with two stunning goals. Danny Welbeck, Nani and Park Ji-sung were the other scorers.

Ferguson delighted with rampant Man Utd

Theo Walcott reduced United's three-goal advantage on the stroke of half-time but Robin van Persie's strike late in the second half-represented no measure of consolation for a dispirited, broken Arsenal.

United keeper David de Gea distinguished himself with a fine penalty save from Van Persie moments after Welbeck had opened the scoring - and in a game of almost unrelenting misery for Arsenal, teenager Carl Jenkinson ensured they have failed to end a game with 11 players in any of their league games this season when he was sent off.

Old Trafford was understandably exultant at the conclusion of such a carnival performance but Wenger now faces defining days of his Arsenal reign before the transfer window closes on Wednesday.

Phil McNulty Chief football writer quote For Wenger it was a performance, or lack of one, that proved the folly of his summer of transfer inaction Read more of the blog

This result underscores the gulf that has opened up between United and Arsenal and Wenger will now seek to address the weaknesses in his squad and replace the departed Cesc Fabregas and Samir Nasri.

Ferguson's faith in the team that won so convincingly against Tottenham was rewarded with another thrilling attack-minded performance.

Arsenal's uncertainty was partly explained by the unfamiliar make-up of their team, but the flaws were swiftly exposed by the manner in which United took the lead. Anderson's lofted pass was inventive but Arsenal's failure to react was ominous for what lay ahead, allowing Welbeck to head past Wojciech Szczesny.

Van Persie then squandered an instant opportunity to equalise after referee Howard Webb awarded a penalty when Walcott tangled with Jonny Evans in the area. De Gea has had a mixed start to his Old Trafford career but he was engulfed by his team-mates as he dived to his right to make a fine save.

And United ensured Arsenal were punished heavily as Young added the second after 28 minutes. Young found space just outside the area and curled a perfect finish high beyond Szczesny's grasp at the Stretford End.

PREMIER LEAGUE'S BIGGEST WINS Man Utd 9-0 Ipswich - Mar 95

Tottenham 9-1 Wigan - Nov 09

Chelsea 8-0 Wigan - May 10

Newcastle 8-0 Sheff Wed - Sep 99

M'brough 8-1 Man City - May 08

Nottm For 1-8 Man Utd - Feb 99

Chelsea 7-0 Stoke - Apr 10

Arsenal 7-0 Everton - May 05

Blackburn 7-0 Nottm For - Nov 95

Man Utd 7-0 Barnsley - Oct 97

Arsenal 7-0 M'brough - Jan 06

Welbeck's game was cut short by a hamstring injury - but there was no respite for Arsenal as Rooney worked a free-kick routine with Young to send a 20-yard free-kick into the top corner as the interval approached.

Walcott halted some of United's momentum when he took advantage of slack marking to shoot beneath De Gea in first-half injury time.

It made little difference amid the carnage of the second half as Arsenal were torn apart amid a torrent of goals, near misses and saves from the desperately exposed Szczesny.

Arsenal survived until the 64th minute when they were undone by another piece of Rooney creation at a set-piece, again linking with Young before dispatching the finish past the motionless Arsenal keeper.

It was the breaking point for Arsenal and they spent the remainder of game in a constant state of siege. Rooney was the creator for Nani with the pass that gave the Portuguese the opportunity to send a flamboyant chipped finish over Szczesny for United's fifth.

Wenger 'hurt' by humiliating defeat

With the Gunners in disarray, Park marked his arrival as substitute by lashing home an unstoppable finish before Van Persie briefly interrupted the one-way flow towards Arsenal's goal by beating De Gea.

It barely seemed possible for matters to get worse for Arsenal, but the agony increased when Jenkinson was sent off after receiving his second yellow card for fouling Javier Hernandez as he raced clear.

Rooney completed his thrilling treble with a penalty eight minutes from time after Walcott fouled Patrice Evra.

And United completed the scoring with their eighth in injury time, Young once again showing his eye for the spectacular with another curling shot.

Wenger cut a despairing figure as he walked back to the dressing room at the final whistle after one of the darkest days of his career.