OXFORD United endured a tough afternoon as they lost ground in the play-off race with a thrashing at the hands of in-form Peterborough United.

The hosts played for half an hour with ten men after Nathan Thompson was dismissed.

But Posh were already 2-0 up by that stage, via goals from Siriki Dembele and Ivan Toney.

It was the least the dangerous home side’s display merited, as they ran a U’s side who had played 120 minutes on Tuesday ragged.

The red card gave the visitors a slim chance of another two-goal fightback, but that was extinguished when Toney grabbed his 23rd goal of the season.

Josh Knight rubbed salt in the wounds in stoppage time to inflict a heavy defeat.

It saw United, whose boss Karl Robinson was serving a touchline ban, slip to tenth before their busy month continues at Burton Albion on Tuesday.

Skipper John Mousinho, top scorer James Henry and Matty Taylor returned in United’s three changes from the midweek defeat to Newcastle United.

There was little to choose between the sides in a tight opening 25 minutes where neither side gave much away.

The game though opened up after the home side were forced into a change, when defender Frankie Kent was forced off with a knee injury.

Marcus Browne smashed a 30-yard free-kick inches wide seconds later, but from then on Peterborough took charge.

Sammie Szmodics warmed Simon Eastwood’s palms from 15 yards, while the goalkeeper will have been relieved to see Dembele shoot wide after the forward robbed Rob Dickie 20 yards out.

The hosts were just getting started, though, and took the lead nine minutes before the break.

It came via a mistake from Cameron Brannagan, who gave the ball away near the halfway line. Szmodics pounced on it and slipped in Dembele to slot past Eastwood as United appealed for offside.

There was controversy three minutes later, when Szmodics threatened to double the lead.

He raced on to Toney’s lay-off, only to go down 25 yards out under pressure from John Mousinho. The referee would have had to show a red card if he felt it was a foul, but felt the Bristol City loanee went down easily.

United’s reprieve might have only lasted four minutes.

After Henry’s ambitious penalty appeal fell on deaf ears, Posh broke at pace to create a big chance for Dembele. His shot was blocked on the line by Sam Long, before Alex Gorrin denied Szmodics’ header and Dan Butler’s shot on the rebound.

Long also made another last-ditch intervention to deny Dembele a tap-in from Szmodics’ inviting cross before United reached the safety of half-time.

They had an opportunity to regroup, but within two minutes of the restart Eastwood was needed to save from Toney’s 18-yard effort.

The only comfort for the U’s was they were only a goal down.

That though only lasted until the 56th minute, when the visitors were caught out by another lightning-fast counter-attack.

Henry almost reached Mark Sykes’s knockdown in the Posh box, but the hosts raced forward and the dangerous Szmodics crossed for Toney to tap-in.

With Peterborough lethal on the break, it looked a forlorn task for the visitors.

But they were handed a lifeline just after the hour, when Browne was brought down on the edge of the box by Thompson.

It saw him booked for the second time in the afternoon and as he came off the former Swindon Town defender, who was involved in an infamous red card for Alex Mowatt at Portsmouth, got involved in a fracas with the U’s bench.

Henry fired the resulting free-kick over before both sides made two changes.

United brought on Nathan Holland and Liam Kelly as they searched for a way back from two goals down, as they had managed against Newcastle in midweek.

But 13 minutes from time the task got even tougher. Toney outmuscled Mousinho to win a free-kick on the edge of the box, before the striker got on the end of Dan Butler’s free-kick to make it 3-0.

Posh goalkeeper Christy Pym made brilliant one-handed saves to deny headers from Josh Ruffels and substitute Jamie Mackie.

It was as close as good as it got for United, who could arguably have done without the nine minutes added on for stoppages.

During the additional time the hosts made the most of another break, as Knight finished off Szmodics’ pass to cap off a rotten afternoon.

Peterborough Utd (3-4-1-2): Pym, Thompson, Beevers, Kent (Mason 28), Ward, Brown (Bennett 67), Taylor, Butler, Szmodics, Toney, Dembele (Knight 67).

Unused subs: Eisa, Boyd, Jones.

Booked: Thompson, Toney.

Sent off: Thompson.

Oxford Utd (4-3-3): Eastwood, Long, Dickie, Mousinho, Ruffels, Gorrin (Kelly 67), Henry (Mackie 79), Brannagan, Sykes (Holland 67), Taylor, Browne.

Unused subs: Stevens, Moore, Thorne, Agyei.

Booked: Mousinho.

Referee: Andy Haines (Tyne & Wear).

Attendance: 8,363 (862 visitors).