Siriki Dembele's second goal of the season for Oxford United claimed a vital three points for the hosts
Oxford United gave their Championship survival hopes a huge boost as they beat promotion-chasing Sheffield United.
Siriki Dembele's first-half strike separated the two teams and lifts Oxford - who put in an excellent defensive second-half display - four points above the relegation zone with six matches left to play.
Sydie Peck came closest to an equaliser for the second-placed Blades who stay below leaders Burnley but remain a point above Leeds United in the automatic promotion places following the Whites' draw against Luton Town earlier on Saturday.
The defeat ends a run of six straight away wins for the Blades, their best run of form on the road in 132 years.
Oxford started the match on the front foot and Przemyslaw Placheta's delightful left-footed cross found Mark Harris at the back post but the Wales international was unable to get good enough contact and the ball drifted out for a goal kick.
The visitors took a while to settle down but midway through the first half, Harrison Burrows got down the left-hand side and struck from range but Oxford keeper Jamie Cumming was equal to it.
Moments later, good work from Ben Brereton Diaz down the right saw him find Tyrese Campbell in the box but his effort from eight yards out was excellently saved by an outstretched leg from Cumming.
Ex-Sheffield Wednesday midfielder Will Vaulks' long throw was then headed on by Ben Nelson at the near post and, after the Blades failed to clear, the ball eventually fell at the feet of Dembele who slotted the ball past the on-rushing Michael Cooper to give the hosts a surprise half-time lead.
Gary Rowett has won seven of his 19 Championship matches in charge of Oxford United since arriving in December
The Blades looked like they received a stern half-time team talk by Chris Wilder, who returned to the Kassam Stadium after spending over five years in charge of the U's from 2008 until 2014.
And three minutes after the break, Peck saw his header cleared off the line after meeting a pinpoint corner from Burrows.
Wilder looked to his bench and made five changes - including the introduction of Crystal Palace loanee Jesurun Rak-Sakyi on the hour mark - in an attempt to get back on level terms and the 22-year-old instantly looked to give the Blades impetus from the wing forcing the U's defence back.
With 20 minutes left, Gus Hamer then found Peck just outside the box but his right footed effort went a whisker wide of Cumming's goal as United threatened to get back into the match.
That was as close as the visitors got to scoring, however, as Gary Rowett's side held on to pick up just their second win in 12 games.
'We had to make it into a fight' - Rowett
Oxford United boss Gary Rowett told BBC Radio Oxford:
"From the word go, we looked on it today. We had to make it a little scruffy, we had to make it into a fight but we know how good a side they are.
"One thing that did help, I thought the atmosphere was brilliant from the start and that made such a massive difference to me, the staff and the players.
"It's nowhere near job done but it gives us a fantastic opportunity to go again on Wednesday against QPR who are fighting for their own points but we've got to enjoy the performance and the desire of today.
"You've got to dig in, do whatever it takes to get the three points, and then put your feet up and watch whatever it is you like on a Saturday night."
Sheffield United boss Chris Wilder told BBC Radio Sheffield:
"We didn't do enough so there's no arguments about the result.
"They started better than us - a team fighting for their lives, they stuck it on us with long throws. We had two or three opportunities before they scored which we should probably take.
"There was an opportunity to gain three points but well done to Gary [Rowett], they deserve their win and obviously an amazing away record comes to an end.
"It's not an attitude problem, we just made some bad decisions. It was a slow pitch, a dry day, and we have to recognise we have to play a little bit quicker and more direct.
"We've got to make better decisions, to do something different. We didn't do the basics right.
"The game's not won on a coupon, the game's won on a pitch, and we didn't do enough to win."
