A famous victory was gained with the Hammers reshuffling the midfield, putting Joe in the middle of the four for the first time this campaign, and Paul says: "Joe certainly had his best game of the season - and he gave us another dimension in the middle of the park.
"He is still trying to regain his fitness after a long lay off.
"He enjoyed it thoroughly, I know that, and we were talking the day before about the challenge of Roy Keane, Nicky Butt, and Scholes in midfield."
Paul was quick to praise the other midfielders, however, with Trevor Sinclair switching to the left - where he had expected to mark David Beckham - and Don Hutchison reverting to the role on the right that he frequently played in for Sunderland last season.
"Joe and Michael relished the challenge in the centre and Don, who has had two or three very good games for the club recently, had a very good game on Saturday," says Paul.
"Trevor worked his socks off down that left hand side, kept the ball well, and was a threat going forward with Paolo.
"Glenn felt we needed to do something a bit different for a number of different reasons and fortunately it paid off on Saturday.
"They are paid by West Ham United to play football and they will play where Glenn feels it is best to put them - it is up to them to do their best.
"Obviously we listen to what they say and look at each player's attributes and try and put them where we feel we will get the best out of them."
Paul does not want the fact that Manchester United had some notable absentees from their line up to deflect from the achievement of winning at Old Trafford, and he explains: "You just have to beat the team that is put out in front of you and it is not as if the replacements were shoddy by any means.
"They've got so many players and Sir Alex has to shuffle them around, keep them happy, and bear in mind if any of them are tired or have knocks.
"Beforehand you start thinking about what sort of team they are going to have and normally it takes two or three seconds to flick through the team sheet.
"But this time it did take a while and the fact that Van Nistelrooy didn't play was certainly pleasing."
Paul says he was as pleased with the performance as the three points and adds: "The manner in which we did it is gratifying as well - we didn't fluke one but played some very good football and I'm sure we'll take a lot of confidence from that.
"You don't go to Manchester and not let them have any chances - they will always create, and to get any kind of a result there you need to defend well, you need your goalkeeper to make a few saves, and you need your players to retain possession of the ball.
"If you give the ball to Manchester United they just flood back at you and that was something we did very well on Saturday - keeping it away from them for long periods."
But he does not want the players to get carried away with one win and concludes: "You spend a day or so thinking about it and enjoying it but then you move on, and it didn't take Arsenal too long to remind us that we are going to have a very tough game this weekend!"