Keeper Reina scooped Arsenal striker Marouane Chamakh's header
into his own net after the ball had rebounded off a post.
His gaffe followed Joe Cole's straight red card on his Anfield
debut, for a reckless challenge on Arsenal defender Laurent
Koscielny in first-half stoppage time.
Kop boss Roy Hodgson admitted: "Pepe has taken it very hard.
"He's a serious pro who believes in himself and the team. He had
played very well considering he had not had a lot to do.
"Pepe has had a shoulder injury but came back from that quicker
than we thought.
"But the negative to it is he's let in a goal he'd otherwise
have kept out."
It was heartbreaking for the hosts, who took the lead early in
the second half through David Ngog's blistering shot - his fourth
goal in three games.
But when Tomas Rosicky's cross was nodded on by Chamakh, it came
back off a post - only for the retreating Reina to bundle it over
the line.
Liverpool veteran Jamie Carragher, 32, insisted: "It's a real
kick in the teeth for any team, even if it had been 11 versus
11.
"But Pepe is the best goalkeeper in the world. He was our player
of the year last season but we all make mistakes.
"It's very disappointing but, at half-time, we would have taken
the draw."
More drama was to follow when Koscielny was given his marching
orders - for two bookings - in injury time.