David Moyes says Jack Grealish missed Everton's goalless draw with Burnley due to illness, days after the Manchester City loanee partied with ex-team-mate Kyle Walker in London. The two England internationals were spotted for a pre-Christmas bonanza last weekend, and while Grealish was absent for the trip to Turf Moor, 35-year-old Walker still featured and didn't seem worse for wear.Following Everton's 1-0 defeat to Arsenal on December 20, Grealish and Walker reportedly hit the capital for a night of frivolity. The pair are said to have racked up a £20,000 bill after going to Winter Winderland, dining at a Mayfair restaurant, partying at a club, and then ending the evening at a strip club in Leicester Square. Fast forward to Saturday and Grealish, 30, was absent from the 0-0 draw against Burnley but Walker had a solid game at right wing-back. The result did little for the Toffees, who are 11th in the Premier League table, whereas the Clarets remain 19th but have closed the gap to safety to six points.Moyes revealed that Grealish trained earlier this week but a "bug" kept him out of the Burnley draw. When pressed on the nature of Grealish's ailment, he replied: "I can expand, but I don’t think I need to. He’s had a bit of a bug, he’s sick. He trained with us on Tuesday and just didn’t feel so good."The Scot also acknowledged that their cause wasn't helped by not having Kiernan Dewsbury-Hall, Jarrad Branthwaite, Illiman Ndiaye, and Idrissa Gueye available, alongside Grealish."No Dewsbury-Hall, no Branthwaite, no Ndiaye is away, so is [Idrissa] Gueye, so we have quite a few players out at the moment. Hopefully, Jack will be back in training, and we will get him back this week sometime," he added.Former Manchester United boss Moyes could not hide his disdain for his side's display against struggling Burnley.He told BBC Match of the Day, "You wouldn't want to watch too much of that, certainly from our point of view. Burnley might have different thoughts but from our point of view it wasn't a good performance. We have been playing quite well recently but today wasn't one of our best. It's a difficult time. Lots of games and different things going on, but I was disappointed that we didn't play better, because we can do a lot better than we played. We go away with a point and a clean sheet so there are some positives to take from it. I'm not happy at all because I didn't come here for a point, I came here to take three, but we never really got going right from the start. I never thought we got into second gear. But when you can't play so well you've got to try and take something from the game and we did do."Conversely, Clarets boss Scott Parker was encouraged with his team's display, despite feeling they should have taken the victory.He added, "I thought we were well worthy of the three points today. We came here understanding what we needed to be and we were every bit of that. The fine margins of what the Premier League is - we didn't put our chances away when we had some real good chances. We're frustrated because we were very, very close today to getting the three points and we've not managed to do that. It's a clean sheet, a point and a good performance and that's what encourages me."Everton will hope to end the year on a high when they take on lowly Nottingham Forest on Tuesday at City Ground, whereas Burnley entertain Newcastle United at Turf Moor on the same date. If results go the Toffees' way, they could be back in the top seven with a win.