"Sterling has got incredible pace. But with Guardiola he is trying to think about the game and understand space," says Martinez, the former Everton manager.
"We've seen two different parts of his work with Guardiola: The first season was trying to give a lot of width, expose defenders in those one-v-one situations.
"This season we've seen something completely different; Guardiola has allowed him to come centrally and he's become a different player."
But Martinez believes there is one part of the winger's game that can still be improved, and cites a Liverpool player as a prime example.
"The next step will be how we're talking about Mohamed Salah, a player who has slowly become stronger and more clever in how to get into the goalscoring positions, and then take them."