Goals from Rigg, Constable, and Williams ensured Oxford United regained top spot in League Two on Saturday afternoon - as previous leaders Fleetwood Town were humbled at rock-bottom Northampton Town.
The Stags took the lead early on, when Mansfield 'keeper Marriot could only palm a shot to Rigg, who had the simplest of tap-ins. The home-side then had McGuire sent off for a high challenge, but got a break when Stevenson smashed a loose ball home in the fourth minute of injury time to level proceedings.
That wasn't it for the first half though, as James Constable netted from six yards in the eighth minute of injury time to put his side ahead, and give himself his 100th goal for Oxford.
The 10-men struggled to get back into the game, and the points were wrapped up half-way through the second half, when Williams finished well to make it 3-1.
It was a sixth win in eight away games for the Yellows, and with Chesterfield and Rochdale also both winning on the road, it ensured they stayed ahead of them both on goal difference after 12 games.
Former leaders Fleetwood fell behind all three teams in fourth, as they conceded an injury time free-kick to bottom side Northampton - who collected their first win in six games.
It was an important win for The Cobblers, who were four points off the pace at the bottom before today. It was perhaps a worse loss for Fleetwood, as just five points separate the top 12 teams now, meaning every game is vital over a busy Christmas period.
Elsewhere, Wimbledon destroyed Portsmouth 4-0, while 22nd placed Accrington recorded an important 2-0 win over Scunthorpe. Dag & Red kept in contention at the top as they moved above Burton Albion after a 2-0 win, while Bristol Rovers and York both drew at home to Bury and Plymouth respectively.
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