Anthony Tonkin was sent off on his return to former club Cambridge in a hard-fought clash at the Abbey Stadium tonight.

League leaders Oxford battled back from a goal down, following an error from Rhys Day, to earn a point.

But with second-placed Stevenage winning by a cricket score at Eastbourne to close the gap at the top to four points, they will feel this was a missed opportunity.

Left back Tonkin's professional foul on Danny Crow when the striker was through on goal 13 minutes from time gave referee Stephen Ross little option.

The challenge was outside the box, and the U's defended the free-kick, so Tonkin, who will now be suspended for one match, may believe he saved his team a goal.

But it was all so unnecessary from Oxford, Jake Wright having lost possession and Jai Reason then threading the ball through to Crow.

The outstanding moment of the game came when Ryan Clarke pulled off one of the saves of the season midway through the second half.

It came when striker Danny Crow let fly with a 30-yard volley.

There looked to be no way Clarke would be able to reach it as the ball sailed over his head and looked set to drop into the goal, but the keeper stretched himself to the limit to arch back and turn it over the bar.

Clarke made a second top-class save from Crow's free-kick staright after the sending-off.

United were without top scorer James Constable, who had taken a knock in training and was not risked.

So up front, Chris Wilder gave new signing John Grant his full debut, alongside Matt Green. It was an attack with plenty of pace.

Cambridge's poor recent form was such that, with their victory over Chester in December now taken out, they had not won since October 31.

However, they took the lead in the 18th minute, and from Oxford's viewpoint, it was a horribly sloppy goal to concede.

Rhys Day has been liable to have one lapse of concentration every game, and he did so again when he was robbed of possession five yards outside his box, by Danny Crow.

Only good covering from Jake Wright halted the danger.

But from the resulting throw-in, Damian Batt gave away a free-kick which was whipped in by Simon Russell, Dave Partridge headed back and centre back Brian Saah knocked the ball in from close range.

Grant and Green were showing signs of a good understanding with some slick link-ups, and Grant's directness was impressive.

Simon Clist produced a great first touch and fierce drive from 30 yards, but keeper simon Brown got behind it.

By now, the visitors were dominating possession, and putting together some eye-cathcing moves.

It was following one, that must have included more than 20 passes, that Green equalised with a brilliantly-worked goal.

Wright delivered a cross from the left, Chris Hargreaves flicked it on with his head, and, as Cambridge's defence came out hoping for offside, Green controlled it skilfully on his chest and shot home on the swivel.

It was his 11th goal of the season. He had been on 11 a week ago, only to lose one goal with Chester's expulsion, and so drop down to tenth.

Oxford were by now totally on the front foot, and just before the break, Adam Chapman nearly scored a second with a 20-yard drive from a free-kick touched to the left. Simon Brown parried it to safety, with some difficulty.

Cambridge had much more of the play in the second half where scoring chances were few at both ends.

After Sam Deering had come off the bench for Chapman, Hargreaves put a difficult shot over, and late on Clist curled a free-kick, intended for someone's head, straight into the keeper's arms.

In injury time, Wright miraculously cleared from under his goaline from Saah's downward header.

But there was an equally astonishing near-miss at the other end, as Deering's effort from three yards was saved point-blank by Brown.

Cambridge Utd: Brown 6, Gleeson 6, Saah 7, Partridge 6 (Coulson 80), Palmer 6, Ives 6, Carden 7, McAuley 6 (Reason 73), Russell 7, Crow 6, Phillips 6 (Willock 69). Subs not used: Beesley, Roberts. Booked: Gleeson, Partridge, Carden.

Oxford Utd: Clarke 8, Batt 6, Day 5, Wright 7, Tonkin 5, Chapman 7 (Deering 6, 64), Bulman 6, Hargreaves 6, Clist 6, Grant 7, M Green 7. Subs not used: Turley, Cain. Sent off: Tonkin. Booked: none.

Referee: Stephen Ross (Lincolnshire) 7 Att: 3,002 (678 from Oxford)