The 35-year-old Buffon came under criticism during Italy's Confederations Cup campaign and was even labelled a "pensioner" by Franz Beckenbauer after the Bianconeri's 2-0 loss to Bayern Munich at the Allianz Arena during the club season.
However, Martina is certain his client will ease towards 40 and possibly even appear for the country during the World Cup 2018 in Russia.
"Gigi can reach 40 quietly and without a fuss," Martina told Radio Sportiva. "He can even make it to the World Cup in 2018. Gigi is an absolute champion and still the strongest goalkeeper of them all.
"The penalty shootout against Spain was unlucky, those were simply unstoppable. A goalkeeper can't really be judged by a shootout."
Martina also feels Italy is back to its highest level following a third-place finish at the Confederations Cup and can be considered one of the favorites to win the World Cup in Brazil next year.
"The Confederations Cup was an event which prepared the team well for next year," Martina said. "Italian football has got back to its optimum level, we are back among the top five in the world."