Don't worry, I'm sure Arsenal will win. They've suffered lose streaks, so all the players must be motivated to win especially Crystal Palace is just a mediocre club. Crystal Palace just lost against Everton yesterday, so they should be lack of stamina.
I also think Arsenal should be able to win their match against Crystal Palace. I know the match might not be an easy one for Arsenal, Crystal Palace will want to win the match, and if they can’t win, they will want to go away with at least 1 point in the match. I haven’t really been impressed by Arsenal's performance in their last few matches, they haven’t been able to secure any wins in their last 3 matches. I am just surprised that Arsenal lost to both Fulham and West Ham. Most clubs now understand Arsenal's playing pattern, they play defensive games, and at any opportunity they have, they end up playing a counterattack. I am sure Crystal Palace will want to do a similar thing, so Arsenal have to be very careful in the match.
Crystal Palace lost to Everton in their match yesterday, but you should know that it's the FA Cup, and most clubs are not always serious about it. Don’t be surprised if their playing pattern changes when playing against Arsenal.