Mauricio Pochettino admits his Southampton side were left 'angry' as they threw away an early lead to lose at Chelsea.
Saints enjoyed a dream start to Sunday's Premier League encounter at Stamford Bridge as Jay Rodriguez punished Michael Essien's mistake to give the visitors the lead after just 13 seconds.
Artur Boruc produced a magnificent save to deny Fernando Torres before the interval and Pochettino's well-drilled side looked on course to thwart Chelsea and possibly put Jose Mourinho's long unbeaten home run at risk.
But 10 minutes after the restart, a scramble in Boruc's penalty area ended with Gary Cahill heading the ball over the line.
An injury to the Poland goalkeeper then meant young Paulo Gazzaniga had to come on, and John Terry promptly headed the hosts in front just four minutes after the Argentinian's introduction. Demba Ba wrapped up the Blues' victory in the 90th minute.
Southampton manager Pochettino was happy with the game up until Cahill headed in the equaliser.
"In the second half, I think we were doing well, I think we were controlling the game before we conceded the goals," he said.
"We are obviously angry with the end result. Overall we are frustrated and disappointed."
After confirming that Boruc was on his way to hospital for scans on his hand and wrist, Pochettino added: "They were soft goals that we shouldn't have conceded.
"But this is a learning process. We're always learning. We're the youngest team in the league."
After a first defeat in nine games at Arsenal, Saints have now lost to two of the title contenders who Pochettino says cannot be split.
"They're clearly two teams that are going to be in the fighting to win the league," he said at the post-match press conference.
"Both teams have their strengths, have their weapons to inflict a lot of danger to their opposition."
Saints have now slipped to seventh in the table after round 13 of the season.