Rooney is just one goal short of equalling Sir Bobby Charlton’s record for England and will be leading the line for Manchester United against McClaren’s Newcastle United on Saturday.
And having worked with the former Everton man during his spell in charge of England, McClaren believes Rooney will only receive the acclaim he deserves once he has hung up his boots.
"However much you may criticise, when he is long gone and finished and you look back, he will be one of the greatest ever to play for England," said McClaren.
"He may not be appreciated now, but he will be in 10 years' time. That is always the way of things - and probably his best is still to come."
McClaren worked with Rooney during his time as Sven Goran Eriksson’s assistant coach and then when he took over as manager in 2006.
That spell included England’s Euro 2004 campaign, when a teenage Rooney burst onto the international scene before suffering an injury in the quarter final against Portugal, and the 2006 World Cup during which Rooney was also involved.
And McClaren believes the 29-year-old can still deliver in a major international tournament, should England secure their place at next summer’s Euro Finals in France.
"People say he has never delivered on the big stage, but I have been involved with him with England," he added.
"In Portugal in 2004, that was his tournament, only for him to pick up that injury. You wonder what might have happened. We thought we had a real chance with this boy.
"As for not delivering in tournaments, it is a team game and too often, the team has not delivered in major finals, so it is very difficult for him. It is the same thing levelled at [Lionel] Messi.
"Footballers are never appreciated at the time, but he will be in 10 years."
Rooney and his Three Lions team-mate will be back in action next month when they face Euro Qualifiers against San Marino and Switzerland.