OXFORD United suffered a big blow to their play-off hopes as they were unable to make the most of their chances after conceding an early Marc Richards strike.

The in-form home side responded well from the early setback, but not for the first time this season were left ruing a lack of ruthlessness in the final third.

They controlled the game up to half time as Chesterfield hung on desperately at times.

Deane Smalley came closest to finding an equaliser as he went through on goal late in the half, only to see his shot saved.

But they were never able to exert the same pressure after the break and Chesterfield held on to claim all three points.

Liam Davis replaced Luke O'Brien in one of two changes to United's starting line-up.

Smalley came in to partner James Constable up front, so Alfie Potter switched to the right flank as Josh Parker dropped to the bench.

The U's were looking for a sixth win in eight games, but they found themselves behind after the first meaningful attack of the game.

On five minutes a ball into the box from Richard Brindley seemed to catch out the hosts' back four, allowing Richards to sweep a finish past Luke McCormick.

It stunned United, who took time to find a rhythm in their search for an equaliser.

Chesterfield goalkeeper Tommy Lee gave them a first glimmer of hope on 15 minutes by dropping a high cross from Sean Rigg.

Constable was just unable to take advantage, but it helped to get the U's going.

For the majority of the half hour leading up to the break Chesterfield were pinned back and looking to slow the game down as much as possible.

Midway through the half another Rigg cross caused problems. Potter had a header blocked and the ball fell to Smalley, who had three efforts smothered before the Spireites finally cleared their lines.

Smalley looked fired up against his former side and picked up a booking for hauling Nathan Smith off the pitch.

The full back appeared to be wasting time, but he was substituted before play restarted.

Barring a free-kick which Conor Townsend curled onto the roof of McCormick's net, it was one-way traffic in the lead up to the break.

Chesterfield defended well, but a clear-cut chance arrived in first-half stoppage time.

A diagonal ball from Scott Davies was misjudged by Neal Trotman. It fell for Smalley to face Lee one-on-one, but the goalkeeper blocked his powerful shot.

The first chance of the second half also fell to Smalley, who spun in the box and had a shot saved by Lee.

At the other end Jay O'Shea jinked past two challenges and bent a shot just past McCormick's left-hand post.

On the hour Tom Craddock was brought on, giving the U's a front four with Smalley and Potter on the flanks.

There was no disputing their attacking intentions, but all too often United were let down by their own impatience.

Several attacks broke down due to a hurried ball forward, rather than looking to build pressure as they had before the break.

It suited a Chesterfield side keen to soak up pressure and protect their lead.

When United did find a way through Lee, who was not tested enough in the second 45 minutes, held firm.

The goalkeeper did well to hang on to a low Craddock shot which flew through a crowded penalty area.

Harry Worley was thrown on as a makeshift striker in the closing stages, but unlike in United's midweek game against Barnet they could not find a breakthrough in stoppage time.

Oxford Utd: McCormick, Batt, Raynes (Worley 87), Wright, Davis, Potter, Whing, Davies, Rigg (Craddock 59), Constable, Smalley (Parker 77).

Unused subs: Brown, Duberry, Heslop, O'Brien.

Chesterfield: Lee, Brindley (Randall 90), Trotman, Cooper, Smith (Whitaker 27), Darikwa (Talbot 66), Hird, Togwell, Townsend, O'Shea, Richards.

Unused subs: Barrington, Clark, Henshaw, Lester.

Referee: Darren Bond.

Attendance: 6,003 (385 visitors).