UNITED 3 (Becchio 44, Beckford 60, Snodgrass 90), NORTHAMPTON 0
United: Ankergren, Douglas, Naylor, Marques, Parker (Richardson 68), Robinson, Howson, Kilkenny (Snodgrass 58), Delph, Becchio, Beckford (Grella 78). Subs: Lucas, Johnson.
Northampton: Dunn, Crowe, Hughes, Dolman, Jackman, Constantine, Guttridge, Osman, Holt (Davis 64), Anya (Larkin 64), Akinfenwa. Subs: Watts, Coke, Walker.
Referee: A Penn
Booked: Dolman (Northampton)
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Leeds United manager Simon Grayson rested central defender Sam Sodje for the visit of a Northampton side, who needed something from the contest to guarantee their League One survival.
Leeds were aiming for an 11th successive home league win and knew that three points could also be enough to secure fourth place in the Play-Offs.
Fabian Delph returned to the Leeds side after serving a two-game suspension and the youngster came within a whisker of opening the scoring inside the opening five minutes with a powerful strike from distance.
United started the contest brightly and Northampton were on the back foot as Leeds played some good passing football.
There was a cause for concern on 19 minutes when Ben Parker required lengthy treatment after a hefty challenge from Abdul Osman.
Leeds went close to opening the scoring on the half-hour mark when Jonny Howson played in Jermaine Beckford, but the United striker was denied. Andy Robinson was also stopped in his tracks by some good defending as he looked to work an opening.
The visitors looked to get plenty of men behind the ball, allowing Leeds to dominate possession, and Northampton goalkeeper Chris Dunn had to be alert to save from Rui Marques.
But Leeds were in front two minutes before the interval when Luciano Becchio converted from close range after a delightful cross from Parker.
With Millwall losing at Carlisle, Leeds were up to fourth place at half-time, and the same game was having implications for Northampton with the visitors kicking off the second period in the League One relegation zone.
The onus was firmly on the visitors after the break, with their League One place under threat, and it was no surprise that they started brightly.
Former United striker Leon Constantine was denied by a good block from Richard Naylor as Northampton looked to press for the goal which could preserve their status.
But that position suddenly became more parlous as Jermaine Beckford netted his 34th goal of the season. Substitute Robert Snodgrass fed Beckford who duly tucked the ball beneath Chris Dunn on the hour-mark.
A mexican wave rolled around Elland Road as a party mood prevailed, and there was a big ovation for Frazer Richardson on 67 minutes when he was introduced as a substitute.
Leeds were coasting towards an 11th straight home league win, but Andy Robinson had an opportunity to make it 3-0 in the 81st minute when he lifted a shot over the top.
Mike Grella was also denied by Northampton goalkeeper Dunn, who came racing off his line when the striker was through on goal.
There was one more moment to savour, though, when Snodgrass added a superb third goal with a scissor kick after some great play from Robinson.