Barkley is back at Everton after a brief and frustrating loan spell at Leeds United, while David Moyes ponders whether to send him back out to the Championship or keep him at Goodison for the rest of the season.
Pienaar told the Liverpool Echo: "I've always had a word with Ross and I still believe he'll be one of the best players in a few years time if he pushes himself. It's all up to himself.
"He has the ability but we can't just keep on praising him, he has to do it himself.
"He's young and I think now that he's back we might need him in the next couple of months because we'll need everyone at the moment and maybe he'll get his chance to play."