Nigel Adkins said his side did not defend their penalty area well enough in the closing stages of their heartbreaking 3-2 defeat to Manchester United.

Saints led with less than five minutes to go at St Mary’s, but afforded their opponents two free headers in the dying stages that resulted in a pair of Robin van Persie goals.

First, an unmarked Rio Ferdinand headed Rafael’s cross against the post, with the rebound falling to Van Persie to slot home.

Then the Dutch striker flicked in Nani’s corner at the near post in added time to give United all three points.

“There’s two free headers inside our penalty area,” said Adkins. “You’ve got to defend your goal better than that.”

The Saints manager added: “The last goal, we’ve got to go and defend and attack that ball better.

“At the end of the day they’ve got two first contacts on the ball from crosses into the box and that’s the annoying thing.”

Adkins also revealed why he had chosen to substitute three of his most effective players, Jason Puncheon , Rickie Lambert and Adam Lallana in the second half.

“We looked at the period of time, with 15 minutes to go, energy,” he said.

“The lads worked their socks off and for me we have a good group of players and a good bench, so why not go and impact it and give us that energy?”