Shaun Maloney's last-gasp goal denied ten-man QPR a priceless win as Wigan earned a dramatic 1-1 draw at Loftus Road after Loic Remy looked to have won it for the home side with a stunning goal.
QPR were forced to play for 70 minutes with ten men after Bobby Zamora was sent off for a needless high challenge on Jordi Gomez.
Wigan struggled to break down the ten men and QPR made them pay five minutes from time with a goal of the season contender from Remy.
However, there was a still a sting in the tail with Maloney scoring with a free-kick from the edge of the box deep into injury time to secure a draw for Wigan.
QPR started brightly and were unlucky not to break the deadlock after just nine minutes when Loic Remy struck the woodwork.
Junior Hoilett chested the ball off to Remy on the edge of the box and he fired in a shot which rattled off the post with Joel Robles in the Wigan goal well beaten.
QPR suffered a major blow after 21 minutes when they were reduced to ten men after Zamora was sent off for a dangerous tackle on Wigan midfielder Gomez.
Zamora caught Gomez on the head with his studs and after lengthy consultation with his assistant referee Phil Dowd showed the QPR striker a straight red card.
Wigan tried to make their numerical advantage count and Callum McManaman twice went close with efforts from the edge of the box, with his first attempt curling over the crossbar and his second shot fizzing just wide of the far post.
Julio Cesar was called into the action three minutes before the break when he was forced to tip James McCarthy's long-range shot round the post but QPR managed to keep them at bay up until half-time.
Harry Redknapp introduced Adel Taarabt ten minutes into the second half and he was quickly into the action crossing for Remy to narrowly head wide of the far post just past the hour mark.
Wigan wasted a great chance to go in front 13 minutes from time when Gomez picked out substitute James McArthur unmarked inside the box, but he headed his effort straight at Cesar.
QPR grabbed what could prove to be a crucial goal come the end of the season five minutes from time with a stunning effort from Remy.
Stephane Mbia led a sweeping counter-attack from inside his own half from a Wigan free-kick to tee up Remy to side-foot a brilliant first-time effort into the top corner to send the home fans into raptures.
Maloney had the final word for Wigan when he curled home his free-kick four minutes into injury time to leave QPR deflated.
A double from Tomas Rosicky had put the visitors in control of the game at The Hawthorns before James Morrison converted from the spot after Per Mertesacker had been sent off for fouling Shane Long.
The win keeps Arsenal firmly in the hunt for a top-four finish and Wenger was delighted with the performance against strong opposition.
"It was a difficult game against a good West Brom side who were really up for it," he said.
"They fought until the last second and we have shown two aspects of our game today.
"One that was very in control and with technical quality, and one that is less known - fighting spirit, a resolute attitude and battling qualities that reflect well the spirit we have in our side.
"I'm very pleased because it was three big points for us."
The Gunners seemed to be coasting to victory until Mertesacker was sent off by referee Howard Webb.
Wenger had no complaints about the decision to dismiss the Germany international but was upset he had to wait to introduce captain Thomas Vermaelen to fill the gap in his back four.
"There were many things that I did not understand, many decisions," Wenger added.
"But we had to take that on the chin and win the game. We couldn't bring him on. I don't know why. I don't complain for the sending off.
"It was a professional foul. He was the last man. It was a penalty and a red card."
Vermaelen has been left out of Wenger's starting XI in recent weeks with Mertesacker and Laurent Koscielny impressing in his place but the Gunners boss was pleased with the Belgian's impact after replacing Gervinho.
"He did very well when he came in," said Wenger. "I have three quality centre backs and I rotate.
"In recent times I played only Koscielny and Mertesacker because we won the games and there was no obvious reason to change. Thomas is a quality player."
West Brom's last win came on March 9 and Steve Clarke's side have now lost two in a row following defeat at West Ham last weekend.
Baggies defender Billy Jones admits the atmosphere in the dressing room has suffered of late but felt the players reacted well following the disappointing display at Upton Park.
"Obviously we are a bit dejected after back to back defeats. We felt we deserved something from the game," he told Albion Player.
"We had chances in the second half, we are disappointed to let in five goals in the last two games.
"We reacted well to our performance last week. It was a better overall team performance. The goals could have been prevented which is frustrating because we thought that Arsenal were there for the taking."
West Brom welcome Newcastle to The Hawthorns next weekend and Jones reckons they squad will take heart from the Arsenal performance into that fixture as they look to keep their hopes of European qualification alive.
"We've taken points off big teams," Jones added. "We feel we are strong at home and we know we have to be at our maximum. "We had a right good go and another day maybe we could have got a draw and a positive result ahead of Newcastle. We can take positives from that performance."
