The pair were involved in Steven Naismith's goal with England defender Baines sliding in a low cross for the Scot, and Martinez is delighted to have the duo dovetailing once more following Pienaar's struggles with injuries last term.
He told the Liverpool Echo: "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."
Pienaar was limited to 23 appearances last term for the Toffees.