Gerrard has by his own admission not hit top gear during parts of 2009-10 - but Capello has no concerns on the day when he will name his provisional 30-man squad for South Africa.
"Some players are really important to the manager and I know Steven very well," Capello said.
"I am sure Steven will be one of our most important players at the World Cup. He knows everything that is expected of him during the games.
"When you start out as manager of a team and try to create one style on the pitch and the spirit of the group, these kind of players are really important."