Baines committed his future to the Toffees by signing a four-year deal earlier today, keeping himself at Goodison Park for what Martinez believes will be the best years of his career.
The 29-year-old has established himself as one of the top full-backs in European football over the last few years, and Martinez believes that he will only get better over the course of his new contract.
"It is an important moment for us. You are talking about January signings and bringing players into the club but no-one will be bigger than having Leighton Baines focusing on being as good as he can be for Everton in the best years of his career," Martinez told PA.
"There were going to be a lot of clubs fighting for those years. He has a World Cup around the corner and you see what a consistent performer he is - not many players can play 38 league games two seasons out of the last three. He has been performing as one the best left-backs in European football and the best is yet to come because now he is in a position where he can enjoy the experience and understanding of the game and affect others around you.
"You look at how important he is with the daily standards, the influence he has with the younger players. I am just looking what Leighton can do in the next four years in the dressing room and it is going to be as good as it gets."
Everton currently sit sixth in the Premier League table ahead of tomorrow's Merseyside derby against Liverpool.