Oxford manager Des Buckingham believed keeper Jamie Cumming had his finest game in a United shirt, as they hold a slender one-goal lead over Peterborough.
A second half goal from Elliott Moore gave the Kassam Stadium side a slender advantage after the first leg clash, with the second leg at London Road on Wednesday.
The visitors grew in strength towards the end, and Cumming was called into action late on.
He said “That was Jamie Cumming’s best game since he’s been here, when we took him on he hadn’t played in nine months.
Oxford beat Peterborough in the League One play-off semi-final first leg on Saturday
Oxford captain Elliott Moore headed home from four yards out in the 53rd minute
‘He slowly found his feet, and it’s pleasing to see the clean sheet. Hopefully it gives him more confidence going into Wednesday.
‘We hold a slim advantage, that’s exactly what it is. We’re only half way through.
‘I’m happy with what I’ve seen tonight, the first half we were very good but the second half there are a few things we need to brush up on Wednesday.
‘Overall to come away with an advantage to their place is what we need, we’re sure Wednesday will be a tough game.’
Oxford started the brighter of the two, and Ruben Rodrigues tested keeper Jed Steer with a shot after just three minutes.
It was the hosts who generally were on top, in the bright sunshine of the Kassam Stadium.
However, it took Peterborough eighteen minutes for their first remote effort of note, when Joel Randall found Ephron Mason-Clark on the left flank, but his shot was collected by Jamie Cumming.
Looking for the breakthrough, Tyler Goodrham fired wide of the woodwork soon afterwards.
Oxford remained the more dangerous of the two sides, and a cross by the impressive Josh Murphy from the left on 36 minutes found its way just over the crossbar.
Elliott Moore directed a header from a corner wide two minutes later, as the hosts continued to apply more pressure.
Peterborough almost took the lead themselves seven minutes after the restart, when substitute Kwame Poku picked up a pass from Jadel Katango, turned and shot in the box and aimed his effort just over.
However, Oxford took the lead a minute later from a corner. Cameron Brannagan connected to the delivery and was able to direct it back into the goalmouth, where captain Moore was on hand to head home from four yards out.
Peterborough pushed for an equaliser, and almost pulled level with twelve minutes of regulation time remaining, when Ricky Jade-Jones flicked a layoff from Randall, that was saved by Cumming.
The Oxford shotstopper was put under late pressure, and spilled an effort by Harrison Burrows that was eventually cleared to safety, but was able to keep a clean sheet.
Peterborough manager Darren Ferguson felt his side were stronger towards the end.
Peterborough manager Darren Ferguson felt his side were stronger towards the end
He said: ‘Once we got our passing game like it has been all season, we controlled the last part of the game and we were unlucky we didn’t get an equaliser.
‘It was tight, nothing was going to be decided tonight and we’ll take it to Wednesday.
‘It will be an exciting game with a great atmosphere at home, and hopefully we’ll get the job done.
‘These semi finals are always frenetic, and you almost want to make them a little dull, especially away from home.
‘Out of possession I thought we were fairly solid, in possession up until they scored we weren’t good enough.’
