The Liverpool captain helped his side move seven points clear of the visitors, with Philippe Coutinho's late strike sealed a remarkable triumph on an emotional day at Anfield, where the 25th anniversary of the Hillsborough tragedy was marked before kick-off.
City had hit back from 2-0 down to level it up and Gerrard admitted that he feared the worst, but Coutinho pounced on Vincent Kompany's poor clearance to win it for the hosts.
One-club man Gerrard, who conducted a rousing post-match huddle with his team-mates, called for cool heads but it was evident how much the result - which keeps Liverpool's destiny in their own hands - meant to him.
"It was emotional, but we need to keep calm," he told Sky Sports. "We've still got four big games to come but that means so much.
"When they got back into the game, you fear the worst at that point. Nothing is won yet, but that was probably the biggest statement we've made so far."
First-half strikes from Raheem Sterling and Martin Skrtel put Liverpool in the ascendancy, only for David Silva to reduce the deficit before having a hand in the leveller, with his shot deflecting off Glen Johnson and Simon Mignolet.
But, with Liverpool having regained the lead in the 78th minute, Gerrard felt the game would never end.
"That's the longest 90 minutes I've ever played in," he added. "I kept flashing back to how long the clock took in big games, cup finals I've played before. It seemed like the clock was going backwards."
The 33-year-old urged caution, though, with four games still to come for Liverpool as they target a first top-flight crown in 24 years.
"The important thing now is not to get carried away with that result," he said. "Nothing's won. Nothing's ours to lose. We've got a week to prepare for Norwich.
"We've seen that these type of games are as tough as the ones today. People said this was the biggest one, but for me the biggest one is Norwich."
