JAMES Constable netted his 100th goal to help Oxford United back to the top of the table as their sensational unbeaten away form continued with victory over ten-man Mansfield Town.
The striker reached the milestone by firing a shot in off the post deep into stoppage time at the end of an all-action first half.
Sean Rigg opened the scoring with his first goal of the season and United were well in charge when Jamie McGuire received a straight red card for a tackle on Danny Rose.
Mansfield hit back against the run of play with a smart finish from Lee Stevenson, but Constable restored the lead on the stroke of half time.
The striker had only just come off the bench to replace Deane Smalley, one of two injuries the visitors picked up, with Andy Whing also limping off.
United exploited the numerical advantage after the break, playing some of their best football of the season.
The third goal their play merited arrived midway through the half, with the excellent Ryan Williams finishing off a flowing move.
It all but ended Mansfield's resistance and United were happy to run down the clock for their sixth away win in eight league games.
Whing and Williams came into the side as two changes from the 2-2 draw with Gateshead a week earlier, replacing Scott Davies and the injured Jake Wright.
Mansfield came into the game on the back of an 8-1 win in the FA Cup at St Albans and they forced the first chance on nine minutes.
Stevenson met Sam Clucas' corner with a firm header, but Ryan Clarke reacted superbly to parry it clear.
It began a breathless first half and when United put their first meaningful attack together, they opened the scoring.
Rose latched onto a loose ball on the edge of the area, beating his man and getting a shot away. Goalkeeper Alan Marriott saved, but the ball fell for Rigg to tap into a gaping net.
Both sides were then forced into reshuffles after losing players in quick succession.
First, Whing limped off with an injury, replaced by Asa Hall.
Mansfield's change was more damaging in the short-term, as McGuire was given a straight red card for a challenge which left Rose writhing in pain.
United looked to take advantage and Rigg, buoyed by his goal, had the beating of full back Lee Beevers.
Williams almost scored a sensational second just before the half hour mark with a lung-busting run down the middle, but his shot drifted wide from 20 yards.
Johnny Mullins, captain in Wright's absence was the next to threaten, heading over at the back post from David Hunt's free-kick.
The game was held up several times as players received treatment and it led to eight minutes added on.
It was an eventful period, starting with the Stags equalising out of the blue when Michael Raynes' clearing header fell invitingly for Stevenson, who lashed in a classy volley.
United had to make another enforced change as Deane Smalley, who had earlier needed attention from the physio, was replaced by Constable.
The striker made an instant impact, restoring the visitors' lead in the 53rd minute of the half. Dave Kitson split the defence with an inspired pass to find Williams, whose cut back was tucked home by Constable to bring up his century.
The visitors looked to go for the jugular when the second half began.
They put together an exhilarating spell of attacking football which sliced through Mansfield's defence, with Kitson revelling in the extra space.
He fed Constable to turn and let fly with a shot which Marriott tipped over while Williams headed just over after an excellent run and cross from Tom Newey.
But while it was 2-1, Mansfield remained a threat.
Jake Speight had a fierce shot tipped over by Clarke, who then presented the hosts with a chance on 64 minutes.
A ball over the top saw the keeper come out to punch, but the ball went straight to Sam Clucas. The midfielder rounded Clarke, but with four purple shirts on the line he shot wide.
Within two minutes United finally had the comfort of a two-goal cushion.
It came from another slick move started by Kitson. The striker's ball inside the full back was perfect for Rigg, who squared to give Williams a deserved goal.
The strike knocked the stuffing out of Mansfield, allowing the visitors to run the clock down with a session of keep ball.
With leaders Fleetwood losing at Northampton, the victory sent Chris Wilder's men back to the top of the pile.
Oxford Utd: Clarke, Hunt, Raynes, Mullins, Newey, Williams, Whing (Hall 19), Rose, Rigg (Ruffels 78), Kitson, Smalley (Constable 45).
Unused subs: Crocombe, Bevans, O'Dowda, Davies.
Mansfield Town: Marriott, Beevers, Sutton, Dempster, Jennings (Meikle 72), Clucas, Howell, McGuire, Daniel, Stevenson (Murtagh 85), Speight.
Unused subs: Deakin, Pilkington, McCombe, Andrew, Rhead.
Referee: Charles Breakspear (Surrey).
Attendance: 3,831 (769 visitors).