The Toffees were hoping for a back door entry to the Europa League by taking out this season's FA Cup but now need to finish as high as possible on the Premier League table to be involved in Europe next campaign.
Moyes was disappointed after the 3-0 defeat to the Latics but is maintaining a positive outlook ahead of the season ruin-in.
"We have to pick ourselves up," Moyes told the club's official website. "We have had a pretty good season, we've not had many downsides but today is a massive one, for me, the team and the supporters.
"We didn't play well and if you don't play well you are going to lose. That's it very simply but that's the case.
"We would normally do better and play better but it was a big off day. Even when we did try to put a bit of pressure on the shots we had were wide or saved."
He added: "The whole team is in it together, not any one player. We will pick ourselves up and bounce back. We had disappointment last year and we will try and do a similar job and finish the season well."