The high-flying Saints missed the chance to climb back into the Champions League places after slipping to a 2-0 home defeat on Sunday.
Koeman has now stressed the importance of the next two matches in the club???s quest to secure European football.
A trip to the Hawthorns on Saturday to tackle West Brom is first followed by Crystal Palace???s visit three days later.
???We know that in the next two games we play a lot for our possibilities for a high position on the table at the end of the season,??? said Koeman on the club???s website.
???I think we???ve had a good week of training. Of course we were disappointed to lose because I think we deserved a better result, but anyway it???s time to go on.
???Normally that (disappointment) is for one or two days at the beginning of the week. Then you see the faces of the players, and the laughs are coming back and then we know that we???d like to win the next one.
???It???s always after losing we like to play as fast as possible to play a better game and to get a better result.
???West Bromwich, in the last few weeks, have done well,??? Koeman continued. ???They???ve had a lot of clean sheets and a very strong organisation in defence.
???If there is coming in a new manager, maybe he changes a little bit the style of play and the players. When he came in, I think it became not easy to beat them.??
???They are really, really strong at set-pieces ??? they???re the team who has the highest number of goals from set-pieces, which will be a difficult part for this Saturday.???