Southampton boss Mauricio Pellegrino bemoaned an "awful day" for Southampton after they were thrashed 4-1 by Leicester City in the Premier League.
There had been signs of improvement at St Mary's Stadium after Sunday's 1-1 draw with Arsenal, when Pellegrino's men were only denied all three points by a late Olivier Giroud goal.
Wednesday's performance could not have been more different as Southampton found themselves 3-0 behind before half-time against former boss Claude Puel's Foxes.
Pellegrino cut a disappointed figure after the humbling loss and called for a reaction when the Saints travel to Chelsea this weekend.
"Really bad game from the beginning to the end," he said. "After conceding the first goal they were getting better and little by little our confidence went down. We gave the ball away all the time.
"For me it is a bit about concentration, not being 100 per cent focused and at this level you cannot be on the pitch giving this advantage. It was an awful day and that is the reality.
"In the Premier League, there are a group of teams where the gap is four or five points and we have to fight. Obviously, we have the same feelings as the supporters.
"Three days before we played a good game but in football in three days everything changes. We need to react now."
The result left Southampton 11th in the table, four points above the relegation zone.