He added: "If you are going to go down there and have a result, you're not playing a New Zealand who are right at the peak of their powers, so of course it's an opportunity."
The All Blacks have won 13 games since Richie McCaw and Dan Carter retired from international rugby, with a 29-40 loss to Ireland in November last year the only blot on their record.
Lewsey started all three Lions Tests on their last tour of New Zealand in 2005, when the visitors were whitewashed 3-0, but he is tipping Gatland to impose a cohesive style on this year's tourists.
"Warren will have a very clear strategy about how he wants to play and, similarly, he will pick players who are most suited to play that style," said Lewsey.
"If you've only got a group of guys for a short period of time it's the most effective way of gelling, and to be really clear what you want to do."
Lewsey joked it would be hard for the 2017 team to be less successful than their predecessors 12 years ago under former England coach Clive Woodward.
"Perhaps we could have been more specific in terms of how we wanted to play," he said.
"Because if you look at the teams in '05, man for man we had a fantastic group of guys, and obviously the Test series spoke for itself in terms of scoreline.
"But I can't help but feel with the talent we had, we underachieved."
