The ball rebounded off Reina after Marouane Chamakh's header hit the goal post in the 90th minute to cancel out David Ngog's powerful strike.
"We defended very well and it's unfortunate to give a goal away at the end," Liverpool defender Jamie Carragher said. "It doesn't matter if you've got 10 or 11 (players), and we're very disappointed it's not even a goal where they've used their man advantage."
The equalizer came after Liverpool overcame Joe Cole's sending off at the end of the first half to take the lead at the start of the second when Ngog beat Manuel Almunia at his near post.
Laurent Koscielny, who was the victim of Cole's red-card lunge, was sent off himself in second-half injury time after being shown a second yellow card for handling.
"I believe we got a deserved equalizer because I couldn't see Arsenal losing a game like this without being deeply hurt," Arsenal manager Arsene Wenger said.
This was Roy Hodgson's first significant challenge as Liverpool manager, having replaced Rafa Benitez after last season's disappointing seventh-place finish.
Hodgson's mission to build confidence was helped by pledges of loyalty from captain Steven Gerrard and Spain striker Fernando Torres, who replaced Ngog in the 74th minute having recovered from the groin injury sustained in the July 11 World Cup final.
Argentina midfielder Javier Mascherano made Liverpool's starting lineup despite telling the club he wants to leave.
Arsenal's main offseason success was rejecting Barcelona's continued pursuit of Cesc Fabregas, but the captain missed the opener with a chest infection.
Despite Fabregas' absence, Arsenal initially looked more confident at a sunny Anfield. In a first-half with limited goal-scoring chances, Arsenal defender Thomas Vermaelen unleashed a fierce 30-meter (yard) strike after five minutes that Reina pushed clear.
Wenger's youthful squad is chasing the club's first Premier League title since 2004 and the Frenchman handed Wilshere his first Arsenal start - four days after the 18-year-old midfielder made his England debut.
Wilshere's main talking point before being replaced in the second half was a lunge on Mascherano in the 40th which earned him a booking.
A similarly reckless challenge saw Cole red-carded with half time approaching, with referee Martin Atkinson punishing the free recruit from Chelsea for a mistimed challenge on Koscielny, who was stretchered off but re-emerged at the start of the second half.
"There was certainly no intention from Joe Cole to foul the player, that's out of the question," Hodgson said. "He's throwing himself to try to block the ball."
Far from jolting Liverpool, the unchanged Reds pushed forward from the whistle at the start of the second period.
Mascherano sent the ball through to Ngog and the French striker, who had a 40th-minute header cleared off the line by Gael Clichy, dispatched a shot that Almunia was powerless to block.
For all Arsenal's attacking exuberance, the failure to sign a new goalkeeper could again prove costly for the team. Almunia missed the ball completely in the 32nd when he flapped at a corner.
Wenger rang in the changes at the hour-mark, with Theo Walcott coming on for Eboue, while Wilshere was replaced by Tomas Rosicky.
Before Reina's gaffe, the Spanish goalkeeper had produced a superb save, tipping over Rosicky's shot that was heading into he top corner.
Chelsea is the early front-runner by virtue of goals scored, after thrashing West Bromwich Albion 6-0 in its opener on Saturday.
Comments