Brendan Rodgers’ side appeared set to secure three points at the Citizens on Sunday after goals from Daniel Sturridge and Steven Gerrard cancelled out Edin Dzeko’s opener.
However, Reina’s error of judgement saw the Reds goalkeeper race off his line and Sergio Aguero curled his strike into an empty net with 12 minutes remaining.
The Merseyside outfit are now 26 points behind Premier League leaders United – and Reina admits Liverpool cannot match the spending power or squad depth of their rivals.
“Right now we can’t compete with the big guns. They have a big edge over us at the moment, both financially and squad-wise,” Reina told Marca.
“There’s a reason they are so many points ahead of us, and it’s not because of one or two better players.”
Reina has been heavily linked with a move to Barcelona in recent weeks after Víctor Valdés’ representatives told the La Liga leaders that the shot-stopper would not be renewing his contract, which expires in 2014.
The Liverpool goalkeeper has made a string of high-profile errors this season – but the Spain international has defended his performances.
“It’s been a strange season for me because I’ve missed lots of games with injury,” he added.
“Some people say I’ve had a bad season, but honestly I think I only had three poor matches, at the beginning of the year.
“This has been the most unsettled season, both personally and as a team, since I joined the club.
“Liverpool is going through a transitional period, with new ideas and a different playing philosophy. That takes time. People have to be patient. It’s normal for us to be erratic.”
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