Southampton manager Ronald Koeman admitted his side let victory slip away as they were beaten 2-1 by Chelsea at St Mary's on Saturday.
Shane Long gave the hosts the lead in the 42nd minute with a cool chipped finish over Thibaut Courtois.
But Chelsea controlled the game after the break and goals from Cesc Fabregas and Branislav Ivanovic saw them snatch victory.
"We did well but it was not good enough to the end and they punished us," Koeman told Sky Sports. "We lost a bit of control in the second half and Chelsea had more possession.
"We were a bit unlucky because some situations were dangerous but not really clear chances to score. The first goal was not a shot, it was a cross that goes in, then they made it 2-1 from a set piece which is disappointing."
Saints had seemed on course for victory after Long's goal and Fraser Forster had broken a club record for the longest time without conceding.
However, the hosts could not add to their advantage and eventually succumbed to their first defeat since January 2.
"To get the second goal you have to create chances and we lost the more ball in the second half," said Koeman. "We didn't have that control in possession and it was different.
"We defended well but it wasn't good enough and they have good players, who play between lines and have good quality and control."
While defeat dents Southampton's European hopes, Chelsea extend their unbeaten record under Guus Hiddink to 10 matches.
"They are playing at a bit of a higher level than they did at the start of the season," said Koeman. "They are more confident and comfortable…but their position in the league is not normal for Chelsea."