Steve Bruce was left in disbelief after seeing his side lose an incredible game at St Mary's.
The defeat ended a run of six wins out of seven for Bruce's high-fliers in what was a thriller.
Amazingly, the Blues had won their previous four away league games, conceding just one goal in the process.
He said: "It was a fantastic game of football and I can't be down on the players.
"But we've made fundamental defensive mistakes for at least three of the goals.
"The whole stadium was stunned and shocked that we were 3-0 down because we'd had a fantastic start.
"We could have quite easily been one or two up before they even managed to get into our half.
"We've looked rock solid in defence recently.
"But for the second goal, the goalkeeper who has played fantastically well recently, looked like he was cleaning windows and then Tiny, who has had a terrific season, hasn't picked up on the fourth one.
"It was something which you see on a playground really - a kick up the middle, we don't pick up and they have a flick on and he's through on our goal."
More Steve Bruce reaction in today's Daily Echo
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