Tommy Mooney's pre-match assertion that United play better against the better teams rang true as they shocked League Two leaders Southend with one of their best performances of the season.

Thanks to first-half goals from Craig Davies and Mooney himself - although his claims to what proved the winner were arguable - the U's gained sweet revenge for their 4-0 hammering at Roots Hall in November.

There were echoes of United's vengeance against Yeovil. Stuffed away, they showed the Glovers in January how far they have come since the first half of the season, and on Saturday they did so again.

It leaves Oxford with the bizarre statistic of having beaten the top two sides in the division and having lost to the bottom two (Kidderminster and Cambridge).

This was a fascinating contest because as well as the eye-pleasing stuff, neat inter-passing and glorious goals, the game of football (and especially this division) is about being able to defend properly and United did that.

Two goals up at half-time, they let Southend back into it through a blunder by goalkeeper Chris Tardif but remained strong and determined, getting players behind the ball and throwing themselves in the way of shots and headers.

Switching from 4-4-2 to 4-5-1 they let the Shrimpers defenders have the ball and defiantly stood their ground, effectively saying to them: 'Break us down if you can'.

But with Paul Wanless outstanding at centre half, and Barry Quinn and Lucas Cominelli effective in central midfield, Southend could find no way through.

Manager Ramon Diaz was back to watch the team and he would have been surprised to see the Oxford Mail Stand so empty, with just 1200 home fans in it.

Southend had brought more than 1800 fans with them, and they made plenty of noise, but United's players were up for the battle, relishing the chance to claim another scalp.

Wales under 21 striker Davies was only starting, for the first time in ten games, because Steve Basham had an upset stomach.

But to my mind, Davies unquestionably adds something to this team. As well as his pace, his aggression and willingness to chase lost causes unsettles defenders.

Southend's leading scorer, Freddy Eastwood, showed great sharpness and an array of tricks but he was the only one of the visitors to pose real danger.

Great work by Eastwood on the left set up a chance for Luke Guttridge in the second minute, but Guttridge scooped his shot over the bar.

Chris Hackett began on the left flank, but when he switched to the right, he was more effective and his runs stretched Southend.

But it was good play by Mooney that set up Davies's opener in the 20th minute. He released Hackett on the right, then screamed for a cross to the near post.

Hackett delivered what he asked, but Mooney couldn't quite get there, yet Davies stuck out a leg to prod the ball over the line at the far post for his sixth goal of the season.

Eastwood responded by beating two players on a diagonal run to the edge of the box, only to be denied by a great fingertip save from Tardif.

With six minutes to go to the break, Hackett won a corner and from it, Oxford scored again.

Lee Bradbury flicked on Cominelli's corner and the ball seemed to go off the knee of Southend right back Duncan Jupp, though Mooney immediately raised his arms to claim it.

"Top of the league - you're having a laugh" sang the United fans.

The visiting supporters were far less jovial, and a fight erupted between a couple of them in the North Stand.

The second half began with Wanless getting in a vital block, and that was to be typical.

Southend dominated possession but were ineffective in front of goal. Eastwood blasted a free-kick over the bar and Tardif made an excellent one-handed save from the prolific scorer's low, angled shot.

But on the hour, Tardif made a bad error, completely missing the ball as he tried to kick clear, although it did appear to bobble. In nipped Eastwood to slide the ball into the empty goal from a tight angle.

Two minutes later centre back Spencer Prior then planted a free header wide from Eastwood's right-wing cross.

It was backs-to-the-wall stuff from United. Wanless and Bradbury both nodded headers off the line, Tardif saved with his legs from Guttridge and in injury time Tardif saved from substitute Wayne Gray, who drove straight at him.

Horacio Rodriguez replaced Davies - who was struggling with a bad cold - with Juan Pablo Raponi, who was of little help defensively.

Yet United held out with great grit and determination, as Alan Hansen would say.