The England captain believes Paul Scholes is wrong to suggest the Manchester United forward has peaked at 28, and thinks the Old Trafford striker can flourish at the World Cup.
Scholes questioned whether his former Old Trafford teammate had already peaked, despite the 28-year-old netting 19 goals in all competitions in 2013-14.
But Liverpool and Three Lions captain Gerrard has backed Rooney - who has entered the past two World Cups with injuries and failed to net at both - to shine in Brazil.
"Paul Scholes is wrong. He's been Manchester United's best player at home and in Europe. He’s been in terrific form," Gerrard said. "What I’ve seen from his performances in the United team, his form has been really positive.
"He’s in a better frame of mind going into this tournament than he’s had going into previous tournaments when he’s had injuries."
In a column for Paddy Power earlier this month, Scholes said: "There's a chance he's worn out.
"Wayne's peak may have been a lot younger than what we'd expect of footballers traditionally. Age 28 or 29 has been the normal 'peak'."
England faces Uruguay, Italy and Costa Rica in Group D at the World Cup.