The Blues duo have formed an impressive left-sided tandem in recent years, despite Pienaar's six-month stint at Tottenham Hotspur in 2011, and Martinez has praised the pair for their understanding on the pitch.
"You get special partnerships in football. Leighton and Stevie have developed that over the years so it is important," Martinez is quoted as saying in the Liverpool Echo.
"Look at the stats. Last season they were probably the most successful partnership in the league and you need that at full flow. If you are a full-back and you have a good understanding you know when and when not to go because you know what he is going to do.
"They can also link up with other players. It's good to have them playing together."
Everton are currently seventh in the Premier League.