It was a game of few chances as Sam Hoskins’ headed goal midway through the first half ultimately proved decisive despite Jason Taylor seeing red on the stroke of half-time.
Taylor was dismissed for an off-the-ball incident but the Cobblers dug deep and after Danny Hylton had missed the resulting spot-kick, they restricted Oxford to very few clear-cut chances.
Wilder was beaming with pride afterwards and praised both the players and the supporters.
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He said: “I’m very proud, both of the club and the players. It’s been a mad week but I think everyone has gone about it in the right way.
“Oxford are going well and they brought a big following but I thought my players and our crowd were outstanding and the club came together as one today.
“We edged the first half and they were always dangerous but we scored a great goal and it was an outstanding effort from my players.”
On Taylor’s red card, Wilder added: “It was a disappointing situation when Jason got sent off.
“I’ve seen the DVD and I can see why the referee has sent him off. I think it was a bit of coming together and Jason has tried to palm him off but he’s just caught him and the referee made the decision.
“But the big thing was that the shape of the team was outstanding as was the work-rate, the effort from everybody was and the way we defended from the front.
“Maybe we could have been a little bit more calm and relaxed in possession when we broke the play up but the longer the game went on the more comfortable we looked.
“Adam (Smith) got the man of the match for the penalty save but I thought the nine in front of him and the shape that they kept and the way the closed gaps and made it difficult for the opposition was outstanding.
“I think they had one shot on target and one shot off target in the second half which is great credit to our shape and our organisation and discipline and the way the players went about it.”
Wilder also admitted he had to work on his side’s shape during the week leading up to the game after their defensive frailties were exploited by Dagenham last week.
“We’ve had a week to discuss it,” he added. “We’ve managed to do a little bit of work on the training pitch.
“We’ve had to work and be more rigid in our shape. Instead of the front three playing a bit loose and free, we tied it down so that the two wide players had to chase back and defend.
“But we still wanted to be a threat going forward and I thought we were. It was a tight game but to play 50 minutes with 10 men is an outstanding effort and it was a true club effort today that got us an important three points.”