Goals from Abou Diaby and Emmanuel Eboue put Arsenal into a commanding position at Bloomfield Road but Gary Taylor-Fletcher replied as relegation-threatened Blackpool played for their top-flight lives.
Taylor-Fletcher felt he was denied a penalty before Robin van Persie made victory safe for Arsenal after 76 minutes.
The afternoon started in dramatic fashion with Almunia’s injury paving the way for the return to competitive action of 41-year-old Lehmann.
It was an unexpected 200th appearance in a Gunners jersey for the German, who was recently coaxed out of retirement to provide emergency cover in the title run-in.
Lehmann had little to do in the first half as Arsenal, with captain Cesc Fabregas also back in their starting line-up, overpowered the struggling Tangerines.
Blackpool had an early chance when Ian Evatt headed over from Charlie Adam’s corner but after that it appeared Arsenal had no intention of suffering a repeat of their previous week’s stalemate at home to Blackburn.
Andrey Arshavin and van Persie both put early shots over before Richard Kingson rushed out to deny Samir Nasri.
It quickly became one-way traffic and the Gunners carved open the Blackpool defence with ease to claim a 17th-minute lead.
Fabregas picked out van Persie with a superb cross-field ball and the Dutchman crossed for Diaby to sidefoot home from close range.
They grabbed a second just three minutes later as Eboue played a neat one-two into the box with Jack Wilshere and then blasted past Kingson.
Blackpool enjoyed a little spell of possession but were unable to test Lehmann and van Persie had the next chance when he controlled another long pass from Fabregas and shot at Kingson.
Kingson needed to be alert again to block an effort by the fleet-footed Nasri after more slick football by the Gunners.
Nasri had another opportunity seconds later when the ball was lobbed back into the box by Fabregas but his volley hit the bottom of the post.
Van Persie took the ball past the outrushing Kingson to set up Diaby but Stephen Crainey got back to tackle.
Some Blackpool fans thought Adam had pulled one back immediately after the restart but his long-range free-kick had struck the side-netting.
The hosts, however, had realised they had little to lose by taking the game to Arsenal and did reply after 52 minutes.
Luke Varney was fouled but play proceeded and Jason Puncheon played in DJ Campbell.
The striker appeared to be fouled by Lehmann as he closed in on goal but the ball ran on for Taylor-Fletcher to fire home.
Blackpool were inspired and poured forward again.
Manager Ian Holloway was furious his side were denied a penalty when Taylor-Fletcher went down under Laurent Koscielny’s challenge.
Taylor-Fletcher then headed wide as Blackpool maintained the pressure but van Persie shot across the face of goal at the other end.
Arsenal made the game safe 14 minutes from time as they quickly turned defence into attack.
Campbell shaped to shoot for Blackpool but Sebastien Squillaci won possession and Fabregas released substitute Theo Walcott down the right.
Blackpool struggled to get back and Walcott crossed low into the box and van Persie made no mistake in front of goal.
Blackpool tried to set up a tight finish but Evatt headed at Lehmann and the Gunners eased to the final whistle.
Wenger has promised his team will give everything in an attempt to pinch the title from Manchester United.
Arsenal could further narrow the gap to a single point if they win their game in hand and beat United when the sides meet at the Emirates Stadium.
It remains an outside bet but Wenger is convinced there is still enough time to overhaul United.
The Frenchman said: “(Yesterday) was only three points and it could help us to keep a chance.
“We have promised ourselves to give everything until the end of the season. There are still seven games. It is a long time – there are many games.”
Blackpool manager Ian Holloway delayed his post-match press conference while he waited to speak to referee Lee Mason in his dressing room.
Holloway eventually emerged to speak to the media around 90 minutes after the game finished.
He said: “It was very amicable. I was very calm, I can’t afford not to be.
“I can’t describe how I feel. How that (Koscielny’s challenge on Taylor-Fletcher) is not a penalty I just do not know, to be perfectly blunt.
“But Mr Mason has given us a couple of penalties before and he didn’t see it as one, nor the handball.
“Those things at this level make huge, huge, huge differences.
“I think the man genuinely gave what he thought he could see. If he wasn’t sure he couldn’t give it.
“It is a bit easier not to be sure against Arsenal but I am sure they have had a few this year when they thought they should have had one.”
Blackpool’s form remains a serious concern after just one win in 12 games and with the team just a point above the relegation zone.
Holloway continued: “I’ll shut up, let’s get on with it and have another go against Wigan next week.
“There are an awful lot of points still to play for.