#2 Midfield partnership issue
Morgan Schneiderlin & Idris Gueye have been the midfield pair preferred by Koeman in the centre of the park for Everton. Playing two midfielders who are defensive minded means that the transition from defence to attack doesn't happen smoothly.
Gueye and Schneiderlin get too involved in shielding the back 3. This means that they are not able to link with the forwards which lead to Everton playing in their half too often rather than moving forward and playing in their opposition's half.
A better option would be to play Davy Klassen, Tom Davies or James McCarthy in a partnership with Schneiderlin, Gueye or Besic which would allow for quick transition from defence to attack and a better link up with the forwards.