By Richard Clarke at Loftus Road
Arsenal went down 2-1 in disappointing fashion at QPR on Saturday.
The team's run of seven straight victories came to an abrupt end thanks to Samba Diakite's fierce drive midway through the second half.
Ironically the winner came just as Arsenal looked like they had properly seized control of the game for the first time.
Adel Taarabt had put the home side in front in the 22nd minute but the visitors were level just before the break when Theo Walcott fired home his 10th goal of the season.
Arsenal went for the win in the second period and, though far from their best, were perhaps unfortunate to lose this tempestuous London derby. Wojciech Szczesny had little to do but pick the ball out of his net on two occasions.
However, even in the worst case scenario, Wenger's men will be level on points with third-place team when the Premier League kicks-off again next weekend.
Despite this hefty blow, their fate remains in their own hands.
The manager made two changes from the side that had beaten Aston Villa so convincingly last weekend.
Laurent Koscielny had dropped out after the warm-up with a knee problem that day and so Johan Djourou stepped up from the bench.
Today the Frenchman was fit again and returned to the side. The other change saw Aaron Ramsey come in for Gervinho on the left of midfield. It was the same side that squeezed out a dogged 1-0 win at Everton in Arsenal's last away trip. The team suggested that Wenger was setting up his side with the same type of performance in mind.
The victory at Goodison Park had been built upon an early goal and Arsenal tried to repeat the trick today.
The visitors bossed the opening stages but could create little in the way of chances. The closest was Robin van Persie's grubber of a free-kick which was gathered at the second attempt by Paddy Kenny.
Arsenal were the form side and seemed set to dominate. But, in fact, QPR would quickly reverse the tide. They put the visiting defence under scrutiny and their best opportunity was clear cut - Taarabt's free-kick was headed over by an unmarked Bobby Zamora from six yards out.
As the first half reached its halfway point the home team had snatched the initiative and were asking all the questions. So you could not argue when they took the lead but, from an Arsenal perspective, their opener was all too easy.
Taarabt received Clint Hill's pass 30 yards out with little on. The Moroccan is a mercurial talent who is blessed with wonderful individual skill. He skipped past his marker, Thomas Vermaelen, and curled his first goal of the season past Szczesny.
Sensing an upset, QPR poured on the pressure in response to the goal but, aside from Jamie Mackie's snapshot, Szczesny was not worried.
And when Arsenal equalised seven minutes from the break, the home side were put back on their heels.
The stretching Van Persie prodded Walcott into space just inside the area. His first effort hit the base of the post but the winger fired in the rebound. It was a crucial strike from a player who has been gaining more influence as Arsenal's season has progressed.
Ramsey and Mikel Arteta fired in efforts as the visitors ended the half in the ascendancy.
After the restart, Kieran Gibbs nudged a header just past the far post then, just before the hour, Kenny had to punch clear from Van Persie's vicious free-kick from the right.
Seconds later the Dutchman raced through to go one-on-one with the keeper. The Arsenal captain has usually been deadly from these situations but this time Kenny pulled off a wonderful flying save.
Still the trend was now set - Arsenal were looking for the win.
However, just as Wenger's men seemed to have found their form, they conceded again. Vermaelen slipped on the edge of the penalty area on the right-hand side. It gave Mackie ample time to pull the ball back to Diakite, who hammered the ball high into the net.
It was both hugely unfortunate and a huge blow.
Wenger immediately brought on Gervinho for Ramsey and his side went in search of an equaliser.
Tomas Rosicky set up Van Persie but the ball was snatched off his toe as he was set to shoot. Although Mackie had a shot blocked, Arsenal were the team with all the urgency.
Eight minutes from the end of normal time, Wenger played his final cards - Alex Oxlade-Chamberlain and Marouane Chamakh came on for Arteta and Gibbs. Arsenal were gambling and trying to crank up the pressure.
They had a couple of half-decent shouts for a penalty but, at the same time, Szczesny had to tip over Joey Barton's chip.
The keeper ended up in the QPR area in the final seconds as the visitors desperately sought the equaliser.
It never arrived.
- Vermaelen Yellow Card
- Gibbs 82
- Arteta 81
- Walcott Goal!
- Ramsey 69
- Song Yellow Card
- Persie (C)
- Oxlade-Chamberlain 81
- Gervinho 69
- Chamakh 82
- Ferdinand Yellow Card
- Diakite Goal! Yellow Card
- Mackie Yellow Card
- Barton (C) Yellow Card
- Taarabt Goal! Yellow Card
- Zamora 90
- Wright-Phillips 90