The Reds' hopes of reaching the last 16 of the competition were dealt a big blow as late goals from Hulk and Sergei Semak sealed a 2-0 victory for the Russian side.
Gerrard admits the result in the Petrovsky Stadium makes it very difficult for his side but he has backed them to respond in the second leg next week.
"If anyone can pull it back, it's us," the 32-year-old told the Liverpool official website.
"We'll have an advantage with our supporters. If they can create the noise they're capable of, get behind the team and we can get an early goal, it's game on.
"But we are disappointed. It wasn't the result we wanted - we wanted an away goal and to try and sneak away with a clean sheet, but if you concede sloppy goals, you get punished and that's what happened.
"Up until the 70th minute against Zenit, the game was under control. It was a tough night in tough conditions. We're disappointed with the two sloppy goals we conceded, but the tie is not over."
Winger Stewart Downing feels the Reds paid the price for a series of missed chances against Zenit.
"They started well and put us under a little bit of pressure, but with the chances we had, especially coming here, it's quite hostile and they had plenty of the ball, but we still had five or six chances to win the game," said Downing.
"But they've got some quality players and they showed that. Hulk was quiet for large periods but he came up with something special.
"The tie is still open. We'll be back at Anfield and we have to try and win the game."
Reds defender Jamie Carragher believes they can draw on the past to inspire them to overcome the two-goal deficit.
"It was a typical European night because you think you are in control and - bang - you are 2-0 down with a mountain to climb," said Carragher. "But it is a mountain the club have climbed in the past and we have to look to do again in a week's time.
"It was a disappointing night but we have a week to dust ourselves down and try to come back and, if we could do it, it would be a great European night."
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