The South Africa international was sold to Spurs for £3million a year ago but injuries have restricted his progress and the 29-year-old has made only 16 appearances for the club.
Pienaar has been linked with a return to Goodison Park but his former Toffees and Ajax team-mate believes that is unlikely, with manager David Moyes working to a restricted transfer budget.
"I'd take him back but I don't think it's realistic," the Holland international told the Liverpool Echo. "They would ask for more money to sell him than they paid us for him and we don't have much more.
"It's up to the manager and the board whether a few players come or not but Pienaar is unrealistic."
Heitinga did not criticise Pienaar for his decision to leave - he also had the chance to go to Chelsea - but he expected the midfielder to have had more game time.
"I played with him at Ajax and he's got a lot of quality," he added. "It surprises me that he's not playing more regularly for them.
"He was injured but he did very well for Everton in the past.
"Everton is a nice club to play for and Steven made the decision to go to another club and it's his right to make that decision.
"You'd need to ask Steven if he regrets it (leaving). The important thing for me is that you're happy and you play.
"I heard in the newspaper he was going to leave and go to another team so you never know what's going to happen."
