Having taken the lead at the Britannia Stadium through Morgan Schneiderlin, Southampton looked on course to temporarily close the gap on the top four to two points.
However, the visitors failed to make their pressure pay and were punished by goals from Mame Biram Diouf and Charlie Adam, but Koeman remains positive about his side's chances of qualifying for Europe.
"Sometimes it's difficult to understand and accept a final result like [that]," he said.
"We know football is about details, but we did enough to get at least a point.
"Maybe in some situations we need to be more clinical in the box, but in general we played well, it's important to keep that until the end of the season.
"The distance [to the top four] is still five points, but we are fighting for a Europa League place, that’s our Champions League, we have to see it like that.
"We are still in very good position in the table."
