The full-back has identified midfielder Gerrard as England's standout player at Euro 2012 so far, with Roy Hodgson's team having surprised many by reaching the quarter-finals as winners of Group D.
Johnson believes Gerrard has revelled in the added responsibility of captaincy, having taken on the role on a full-time basis when Hodgson took charge last month.
"Steven has been a fantastic player for many, many years, but with the armband I think he feels he needs to step up just that tiny bit more, and I think he's done it more than anyone so far," Johnson told reporters at England's training base in Krakow on Friday.
England face Italy in Kiev on Sunday aiming to reach the semi-finals of a major tournament for the first time in 16 years, and Johnson senses supporters in Poland and Ukraine as well as back at home are getting behind the team, with ITV's coverage of the final group match against Ukraine on Tuesday attracting a reported peak audience of 18.5million.
Asked if a new bond was developing with the fans, Johnson said: "I'd agree with that. I've just been told about the record rating of viewers for the game, the fans are there to support and it feels like we're a big, tight unit."
Johnson believes the competition is wide open now that it has reached the knockout stages.
"Any team in the tournament has got a chance of winning it," he added.
"The first objective was to get out of the group, we did that very well by winning the group, so now it's a one-off game and in a one-off game you can beat anyone."
Johnson was speaking before England's latest training session, in which all 23 members of the squad took part.
That included Ashley Young, who suffered a knock to the shin in Tuesday's Group D win over Ukraine, and Jermain Defoe, who is back with the squad after flying home to attend his father's funeral.
It was impossible to glean England's likely starting line-up from a practise exercise between those wearing bibs and those not during the open part of the session, with players who started against Ukraine scattered among the two teams.