The Daily Mail reports how the 29-year-old South African international moved to north London in a £3million deal last January, but a succession of injuries has limited Pienaar to just 16 first-team appearances.
Spurs boss Harry Redknapp is a huge admirer of Pienaar's, and recently quashed speculation suggesting he was poised to leave White Hart Lane.
However, the midfielder has been linked with a return to Merseyside, despite the fact that Everton are restricted to a limited transfer budget.
"I'd take him back but I don't think it's realistic," Heitinga 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."
The Dutch defender did not criticise Pienaar for his decision to leave Everton, but revealed he expected his former teammate to have had more game time at Tottenham.
"I played with him at Ajax and he's got a lot of quality," added Heitinga. "It surprises me that he's not playing more regularly for them.
"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."