Peterborough United suffered a third successive defeat in Sky Bet League One as leaders Brentford recorded a 3-1 victory at a rain-soaked London Road as the beginning of 2014 started in defeat for Darren Ferguson's men.
It was Nicky Ajose, restored to the starting line-up following a successful loan spell at Swindon Town, that had the first effort of the game, but his 30-yarder flew over the crossbar.
However, it was the Bees who opened the scoring on 13 minutes as Saunders was upended in the box by goalkeeper Bobby Olejnik with referee Mr Madley quickly pointing to the spot. Adam FORSHAW stepped up and coolly scored from the spot.
Assombalonga curled a free-kick wide of the target on 17 minutes as Posh tried to make a quick response. The Bees were looking dangerous in attack and should have been two goals to the good on 19 minutes as a low cross to the back post was somehow turned on to the post by a combination of Donaldson and Ntlhe from three yards.
Ntlhe wanted a penalty kick at the other end as he took a tumble under a soft challenge from Donaldson, but nothing was given by referee Mr Madley.
Ajose fired wide with the aid of a deflection on 29 minutes and from the resulting corner kick, Ntlhe glanced a header wide of the far post. On 32 minutes, Posh drew themselves level and it was a stunner from Jack PAYNE, who let fly from 30-yards with the shot crashing against the underside of the crossbar before finding the back of the net leaving goalkeeper Button stunned.
On 36 minutes, the Bees were back in front and once again it was an effort from range, this time Sam SAUNDERS collecting the ball 25-yards from goal and he rifled a shot past Olejnik and into the bottom corner.
Forshaw fired wide from eight yards as a corner was only half cleared as the Bees pressed for a third goal before the break.
On 48 minutes, the Bees were awarded another soft penalty kick as Donaldson was upended in the box. The referee appeared to wave away protests, but the linesman indicated a spot-kick, but this time, Olejnik saved Forshaw's low penalty kick.
Swanson curled a shot over at the other end after a swift Posh counter-attack as the game became open with attacks swinging from end to end.
Nicky Ajose was replaced by Shaun Jeffers just before the hour mark as Posh made their first substitution. Diagouraga was booked for a very late challenge on Payne on 61 minutes, some referees would have given a red for that.
Grant McCann replaced Swanson on 64 minutes. Trotta was denied at the second attempt by Olejnik as the Bees front man cut inside from the left.
On 74 minutes, Button denied a left-footed McCann free-kick after Jeffers was upended by the already cautioned Reeves. Kyle Vassell replaced Little in the final Posh change with Posh going to three at the back.
Assombalonga fired wide of the near post from long-range after a good set-up from McCann on 86 minutes. Olejnik produced a fine stop to deny substitute Dallas in a one v one situation, but he was powerless moments later as the Bees wrapped up the game with DONALDSON tapping home from close-range.
Final Score: Posh 1-3 Brentford
Posh: Olejnik, Little (sub Vassell 77min), Ntlhe, Brisley, Bostwick, Swanson (sub McCann 64min), Payne, Anderson, Newell, Ajose (sub Jeffers 60min), Assombalonga. Unused subs: Day, Knight-Percival, Grant, Conlon,.
Brentford: Button, Forshaw, Craig, Dean, Saunders (sub Dallas 60min), Douglas (sub Diagouraga 40min), Donaldson, McCormack, Reeves (sub Logan 77min), Bidwell, Trotta. Unused subs: Lee, O'Connor, El Alagui, Logan, , Fillo.
Attendance: 6,343 (1,001 Brentford fans)