After 114 caps and 21 goals for England, Gerrard, 34, announced his international retirement on Monday.
Gerrard was one of Liverpool's most consistent players as they finished second in the Premier League last season.
"It's how well the manager coaches him really. I think there's still another two years left in Steven Gerrard," Rush said.
"It's not just about physically, I think being in the dressing room before that, motivating people, getting people going and that's what he's all about. He's a leader and we need those leaders.
"Even if they're not producing the best on the pitch we need them in there. Without a doubt if the manager treats him well he's got another two years left in him."
Rush said Gerrard's international retirement was great news for the club, with it possibly extending his Liverpool career.
"What we should remember is how good Steven Gerrard was for England, that's his decision and we've got to respect that, but for me, I think he could have played on," Fowler said.
"He was voted one of the best players in the Premier League last year, voted by all his peers, and that tells me that he's still highly thought of and still very much good enough to play for England, so it is a sad day, but let's respect Steve's decision."
