Mark Hughes was frustrated by the "soft" late penalty that saw his Southampton side surrender a winning position in Monday night's 2-2 draw with Brighton.
Pierre-Emile Hojbjerg's stunning opener and Danny Ings' penalty had given the Saints a 2-0 lead at St Mary's and they were on course for their first home win of the season.
After Shane Duffy's 67th-minute reply, Brighton were awarded an injury-time penalty when the defender went down under a challenge from James Ward-Prowse and Anthony Taylor pointed to the spot.
Glenn Murray slotted home from the spot, but Hughes was adamant that Duffy went to ground too easily.
He told Sky Sports: "As always, I question the penalty decision because I thought it was a little bit soft.
"I don't think there was too much contact and I think the guy has thrown himself to the floor.
"The referee has deemed that worthy of a penalty.
"We are disappointed. We got ourselves into a winning position - a deserved one, I felt for the efforts up to the penalty we had - and we were quite comfortable.
"We needed just to keep that two-goal cushion for a little bit longer than we were able to and then, as the half progressed, we maybe got a little bit anxious to protect what we had.
"Clearly they were going to throw balls into our box and hope something broke for them.
"Credit to them. They had a real go in the second half and they had to. They had nothing to lose and were taking chances and they got their reward."
Southampton have now thrown away 26 points from winning positions since the start of last season, more than any other team in the Premier League in that period.
And Hughes insists the players must learn from the agony of Murray's late goal.
"We've got to find a way to manage the game better than we are doing at the minute," he added.
"We've had a number of winning positions where we needed to manage the game to a conclusion and at the moment that's a little bit difficult for us.
"It's understandable up to a point. Our record at home isn't good and for long periods today, the performance was fine. We created some good opportunities and we should have been 2-0 or 3-0 to the good before they got back into the game.
"You've got to take your chances and see the game out to a conclusion. We weren't able to do that.
"It's a lesson - and a harsh lesson, if we are honest."