Southampton were the architects of their own downfall in their latest fixture against Manchester United.
The Saints lost 3-2 to Manchester United in their most recent outing, and Maya Yoshida's misplaced back-pass was one of the key reasons for the defeat.
Yoshida under-hit a pass to Maarten Stekelenburg, and it allowed Anthony Martial to nip in and score his second goal of the match.
That effort put United in front on the day, and Koeman was left fuming with the mistake, as it went against what he has repeatedly told the team in training.
“Every day we tell the players play that ball, and don’t play the ball back to the goalkeeper," he fumed. “I will tell them the same story again.
“I hate always players, and it’s in general, not to criticise one of the defenders or Maya who did that mistake, I hate players who play always the ball back to the goalkeeper. Play the ball in the space in front. It’s always a risk. There is nobody in time for the goalkeeper to play the ball back."
Prior to Yoshida's mishap, Southampton had been well in the game and were giving United a thorough test, with plenty of their play looking threatening.
However, once Martial put the Red Devils in front they visibly grew in confidence, and the Saints struggled to match them for the rest of the contest.
As a result of the defeat, Koeman's side sit in 16th place in the Premier League table, and they cannot afford to give away any more sloppy goals if they are to get back on track.