The Saints boss made it clear last Saturday that his side had to pick up three points away to Stoke City, with the team duly obliging as they recorded a 2-1 victory, and Koeman explained that the stakes are just as high again this weekend.
"We knew our situation before the Stoke City game. It was a must-win game and I think the same is for this weekend, because we know the position in the table, we know the points and if we're still fighting for Europe I think we have to win.”
Southampton head into the match in seventh position, one place above Liverpool by virtue of goal difference, but having played two games more.
Koeman believes three points would send them into the international break in a strong position in the battle for Europe.
"We spoke to the players about the schedule and this is the last one before the international break and, of course, if you get a win against Liverpool that makes a big step forward,” he said.