The north Londoners are level on points with PSG but behind them on a head-to-head record.
Wenger's side were on course to wrap up top spot in Group A when they led 2-1 late in the second half at the Emirates Stadium on Wednesday.
But Lucas's 77th minute header was deflected into his own net by Gunners winger Alex Iwobi and Arsenal were unable to find a winner.
That leaves the north Londoners level on points with PSG but behind them on a head-to-head record, meaning the French team will take first place if they win their last group match, against minnows Ludogorets on December 6.
Arsenal travel to Basel on the same night and Wenger conceded it doesn't look likely they will take pole position following their third successive draw in all competitions, meaning they will probably get a tougher tie in the knock-out stages.
"It's not over, but we have a 90 percent chance to finish second," Wenger said.
"We wanted to finish first. We haven't lost a game in this group so we have done well, but we haven't finished the job.
"We dropped off after it was 2-1. We didn't maintain the pressure and paid for that.
"It's frustrating. We were a bit passive on the corner for their second goal."
Arsenal know only too well how damaging it can be to finish second as a series of tough draws have led to six consecutive last-16 exits.
But Wenger tried to remain upbeat and insisted the quality of some of the teams finishing second meant even group winners couldn't be guaranteed an easy draw.
"Will it be bad for us? We have to wait and see," he said.
"If you finish first you play the second game at home, but you look at the groups and it's difficult to tell what is better.
"For me it's more frustrating not to win the game but they are a team with top technical quality."
After a strong run that raised hopes of sustained challenges for silverware at home and abroad, Arsenal have looked lethargic in lucky draws against Manchester United and PSG.
Wenger knows his side have been below their best over the last week, but he doesn't expect the dip to last.
"We have not lost but we have lost a winning momentum a little bit," he said.
"There is a special spirit in the squad. We are unbeaten for 18 games and sometimes you go through a period where you are a little bit less effective.
"It's up to us to transform the draws into wins, but there is no reason to panic."
PSG could easily have finished with victory as Edinson Cavani squandered two late chances, but boss Unai Emery was happy enough with a polished performance that puts his side's European destiny in their own hands.
"If we are to analyse the two matches against Arsenal I think that we deserve to be first at the moment," he said.
"It was a good test and I'm pleased with the way the team responded.
"Arsenal have some good players and are set up well. We did very well against them and our best players showed great personality.
"The players met my expectations. It was a terrific performance and it's important now that we build on this in our next fixtures."