The 1-0 victory at Old Trafford saw Sir Alex Ferguson's side leapfrog the Gunners at the top of the table after Park Ji-Sung's winner gave them all three points at Old Trafford despite Wayne Rooney missing a penalty.
Ferdinand says it was a crucial victory ahead of Sunday's trip to champions Chelsea and says it was the perfect way to start mounting a serious challenge for the title.
Bright spark: Park Ji-Sung celebrates after bagging the winner against Arsenal in the clash at Old Trafford
The United defender said: 'It's a big result. It's not a defining result for the season, but it's a big result.
'It's against one of the teams that are at the top of the table. Last year we probably didn't do as well as we should against the top teams. This is a good way to start.
Laying down a marker: United star Rio Ferdinand
'When I look around the changing room Isee a fantastic bunch of players. I never doubt them or what they arecapable of. If we concentrate and are focussed on doing the things weare asked, we are difficult to play against.'
'I thought we did well. We pressured them high up the pitch. One of the main things that we wanted to do was to go out and make sure we got in their faces and put pressure on them, not give them time on the ball.
'With a team like Arsenal, if you give them time on the ball then they will hurt you because they have got quality players all over the park. We tried not to give them time.
'I have always maintained it is notjust about defending as a back four and a goalkeeper. We score togetherand we concede together. If we are defending right from the front weare a hard team to play against.'
Victory extended United's unbeaten start to 16 matches, a new club record, not that Ferdinand is allowing himself to look too far ahead, or read too much into statistics.
'It is not about trying to go through the season unbeaten,' said the England skipper. 'It is about what you finish up with at the end of the year.
'This was a very big result for us. It is not a defining result but it is the kind of result you are looking for against one of the teams who are also at the top of the table.
'Last year we probably didn't do as well against the big teams as we should have. This was a good way to start.'
Safe hands: Manchester United goalkeeper Edwin Van der Save punches out the ball during an Arsenal attack
Ferdinand admits he was alsodelighted United kept a clean sheet and says it is vital they continueto do that if they are to win the championship this season.
He added: 'To win titles you've gotto be on top form all the time, not just defending as a back four andthe goalkeeper. It's the team. I always say that. Whatever happens in agame, we score together and we concede together. If we're defendingfrom the front then we're a hard team to beat.'
United manager Ferguson praised his team's performance but admitted Rooney's fluffed spot-kick could have been costly.
'Wehad to play well, in these major games you want to perform and I thinkwe did tonight, particularly in the first half we did very, very well,'he said.
'It was anunusual penalty, normally Wayne always keeps them down, I've neverknown him to hit one over. That gave Arsenal a bit of impetus but wedefended very well, the back four were fantastic tonight, absolutelymagnificent.'
As forthe match-winner Park, the Scot said: 'Park's record against Arsenal isvery good, he is in fantastic form, the lad. Unfortunately we're goingto lose him to the Asia Cup for seven matches, which is disappointing.'
Manchester United 1 Arsenal 0: Park Ji-Sung swings it as Sir Alex Ferguson's men go top to slide Gunners into second Arsenal teenager Jack Wilshere holds his own in a man's game at Old Trafford Old Trafford defeat proves Arsenal's familiar failings still dog Arsene WengerPREMIER LEAGUE LIVE: Manchester United 1 Arsenal 0 - the action from Old Trafford as it happened MANCHESTER UNITED FC