The England defender and the South African winger have formed a devastating tandem for the Blues in recent years, dovetailing down the left side of the Blues' attack.
Baines made 32 appearances last season and contributed four assists and five goals, although Pienaar played just 23 times as his campaign was blighted by injury.
Both players were on show for the Blues as they drew 2-2 with Leicester City on Sunday, and it was the left-back who created the second goal for Steven Naismith with an incisive low cross into the area.
The initial ball was played wide by Pienaar to his teammate as the pair revived their partnership, and Martinez was delighted to see them back in action down the left for his side.
After watching Baines and Pienaar play together at the King Power stadium, the Toffees manager claimed that the duo will be key for his side this term.
The Liverpool Echo quotes him as saying: “You get certain partnerships over the park that shine and click.
“Leighton and Stevie, when they are combining together, make a real difference and the second goal at Leicester comes from them.
“The way that they break through the opposition is a joy to watch and we need Leighton and Stevie to be fully fit throughout the season because they are a big part of our attacking play."
The Spaniard was also keen to highlight the individual performance of Pienaar, who turned in a "beautiful" performance, according to Martinez.
"His link up play and touch is beautiful to watch and it was a really good performance," added Martinez. “Everything he did was with a real purpose, everything he did was at his very best level.
“Now we need to make sure we get him back up to a 90 minutes level because a player like Stevie, we need him on the pitch for the full game.”
Aiden McGeady had earlier put Everton ahead before Foxes striker Leonardo Ulloa scored on his debut to level things up for Nigel Pearson's side.
Naismith's effort looked to have given the Merseyside outfit the points, but Chris Wood struck a late leveller to give the newly-promoted side a share of the spoils.
Everton face Arsenal on Saturday evening, and the Blues will be looking to strike a significant early blow in their hopes of landing a finish in the top this season.