Heitinga has a stiff knee while Pienaar suffered an ankle problem in the draw at Chelsea last weekend.
Mikel Arteta is again ruled out through suspension while Tony Hibbert remains sidelined with an ankle problem.
Meanwhile, Moyes has rounded on Newcastle for dismissing Chris Hughton and says club bosses should follow the example set by Manchester United and Arsenal.
Hughton was replaced by Alan Pardew this week despite leading his team to 11th place in the Barclays Premier League after promotion.
Moyes will take charge of his 401st game for Everton against Wigan since joining in 2002.
He said: "Losing your job is a concern to all managers.
"But I don't think everyone has treated their managers the way Newcastle have done. Chris Hughton did a brilliant job and I defy anyone could have done better in the time he was in charge. He took them to promotion and put them in a good position in the league.
"If you look at Sir Alex Ferguson and Arsene Wenger they have been given a good chance to stabilise, build the academies and get the young players through.
"They have set the foundations for the long-term future. People should look at those clubs under those managers and see how well they have done."
Moyes has been widely praised by the football community for his work at Goodison Park but he gives a modest assessment.
He said: "I am not sure how much I have achieved. I think I have done a steady job. I still have a lot to do.
"I will be satisfied if I think I can get the team to cup finals, maybe winning them or getting in Europe.
"I want to be winning things and challenging the big teams at the top. I still believe the best is yet to come and the good times are not that far away."
Wigan manager Roberto Martinez is confident his players have the character to cope with the pressure of finding themselves faced with another relegation battle.
The Latics have not been able to rectify inconsistencies in their results which caused them difficulties last season and once again find themselves in the bottom three.
A busy period over the next month will not decide their season but a healthy return of points would make things easier for Wigan going into the new year.
Martinez has, probably wisely, not set his squad a target haul from matches against Everton, Aston Villa, Wolves, Arsenal, Newcastle and Bolton.
But he is certain they have the mental strength to stand up to the pressure and pull away from the relegation zone, as they did towards the latter end of last season.
"I am not looking for a return in points, I am looking how we can reflect a bit more in the scorelines our good performances on the pitch," he said.
"There have been too many times when we have been so close and those little margins are the ones we need to correct over the next few months.
"We have a huge advantage in that we are a young and talented group and we don't believe what the table is saying.
"We believe in our own ability and we believe in what we are capable of doing so we set our own targets.
"It is important we don't get too pessimistic because we are third from bottom with the same points as fourth from bottom (Fulham) but we should not get too optimistic if we are fifth from bottom.
"The differences are minimal and you can't drop your standards but I think the squad is responsible and mature enough now to understand the needs we have this season.
"We have a fantastic challenge and I don't see it as a pressure point at all, I see it as an opportunity to start getting rewards."
Striker Hugo Rodallega makes a welcome return having served a three-match suspension for his sending-off against Manchester United at Old Trafford.
Source: DSG
