The Latics held a seven-point advantage over Harry Redknapp's strugglers going into Sunday's Barclays Premier League match but the London club improved steadily following Bobby Zamora's early dismissal to eventually take the lead through Loic Remy with five minutes remaining.
Wigan looked beaten but Shaun Maloney stepped up to curl home a sumptuous free-kick beyond Julio Cesar three minutes into time added on at Loftus Road.
Martinez's men remain in the bottom three but have a game in hand on 17th-placed Sunderland, who lost at Chelsea, while QPR's tally of 24 points keeps them in 19th place with six games still to play.
Martinez told Sky Sports 1: "It's a great point because we were 1-0 down and a late goal like that is a point gained, there's no two ways about it.
"But overall we were very poor and I think that's the worst performance we've had this season. We were cagey.
"If anything the sending-off went against us. We are a team that enjoy having the ball and we can open teams up but we made it a hard task.
"The players know that they haven't done things as well as they should have done but that result is very, very important."
Zamora was shown a straight red card for his 21st-minute foul on Jordi Gomez but Martinez feels the decision worked to the Hoops' advantage.
He added: "It was a horrific challenge. I know Bobby Zamora is not a dirty player but Jordi Gomez is very fortunate - he could have been majorly injured.
"It was the right decision. As much as you don't want to see red cards, that was as much a red card as you are going to see.
"We are a team that concentrate on ourselves and what we do with the ball but for some reason today [Sunday] the tension and the meaning of the game got the best of us.
"The sending-off gives an opportunity for the home side to be the underdogs and the crowd were magnificent with them so we were cagey.
"All of a sudden we allowed ourselves to be frustrated and that's the worst thing in football.
"In football you can win, lose or draw but you have to be yourself and impose yourself but we couldn't do it."
Redknapp, meanwhile, took the opposite position on Sunday's match, praising his side's gritty performance despite seeing a lead earned against the odds taken away in "cruel" fashion.
He said: "It couldn't have been more cruel today [Sunday]. We deserved to win with 10 men.
"You try not to give free-kicks away but people are so anxious to win the ball, sometimes over-exuberance can get the better of you.
"We cleared the first free-kick and then we should have kept the ball down in their corner. But there was one more attack and they got a free-kick.
"It's just unbelievable. The players were fantastic today [Sunday] and just worked their socks off. You can't ask for more than that."
The Rangers boss had not yet spoken to Zamora following his dismissal but he knew the former Tottenham striker would be feeling guilty enough before any further admonishment.
"I think it looked like a red card," he added. "Bobby's not a malicious player but it was a clumsy challenge - his foot was high.
"It was a reckless challenge and it's not like Bobby to do things like that. He's not a reckless player.
"He got the red card and then we were down to 10 men against a team that likes to pass the ball but we always looked the more threatening.
"I always thought we were going to get chances and then Remy got that great finish.
"Then... with 10 seconds to go in the last minute of four minutes of added time... it couldn't have been more cruel.
"No one's more sorry than Bobby but we've have beaten them today [Sunday] with 11 men, I'm sure. Even with 10 men we should have won the game."
QPR must reign in the seven-point gap on safety with positive results from games against Everton, Stoke, Reading, Arsenal, Newcastle and Liverpool.
Redknapp added: "We've shown spirit every week since I've been here and I can't ask for more than what they've given.
"The players I've brought in are doing great and have scored goals. Andros Townsend was magnificent today [Sunday] and Jermaine Jenas worked his socks off in the middle of the park.
"We're a much-improved team but when you're playing catch-up all year like we have then it's difficult.
"Today [Sunday] I'm sure they'd almost given up with 10 seconds to play but they scored. You need a bit of luck sometimes and we didn't get any today [Sunday]."