The Toffees suffered a narrow 1-0 defeat to Bournemouth away from home at the Vitality Stadium in the Premier League.
Junior Stanislas’s goal midway through the first half proved to be the difference between the two sides.
Koeman has taken to Twitter to give his reaction to Everton’s defeat to the Cherries.
In the 2half we showed how you need to start the game! Still disappointed our first defeat !— Ronald Koeman (@RonaldKoeman) September 24, 2016
Disappointed today! Fighting second half till last minute but is was not enough.— Jan Kluitenberg (@jankluit) September 24, 2016
Over the course of the 90 minutes at the Vitality Stadium on Saturday afternoon, hosts Bournemouth had 53% of the possession, took 12 shots of which only one was on target, and earned five corners, according to BBC Sport.
Visitors Everton had 47% of the possession, took 13 shots of which just two were on target, and earned three corners, according to BBC Sport.
Everton are fifth in the Premier League table at the moment with 13 points from six matches, five points behind leaders Manchester City.