Chris Wilder believes his side were the victims of a smash and grab raid as they went down 1-0 at Roots Hall.
Ryan Leonard's first goal in 17 months made it a losing start for Oxford`s controversial new goalkeeper Luke McCormick at Southend United.
The controversial U's shot-stopper was making his first Football League appearance since being jailed in 2008 for causing the death of two young children by dangerous driving.
He served half of a four year and seven month sentence and was handed a hostile reception on his return to the professional game by the Roots Hall crowd.
And he was hardly troubled between the sticks until Shrimpers substitute Ryan Leonard headed home an 85th minute cross from Michael Timlin to earn the home-side a 1-0 win, much to the frustration of Oxford boss Chris Wilder.
"If anybody had been here and watched the game they would be amazed at the result and I have smashed the players in there," said Wilder.
"If they expected me to come in and say how well they've played and how many chances they've created they've got another thing coming because the bottom line about playing a game of football is how you get over the finishing line which Southend have and we haven't."
But Wilder did have words of praise for McCormick.
"Obviously it was Luke McCormick's first game and he has just gone about his business and played football," said Wilder. "His debut has been a calm one and he did everything neat and tidy but he is part of a team that has lost at no fault of his own."
Southend boss Paul Sturrock was particularly pleased to see Leonard end his goalscoring drought, which started in August 2011, saying: "When I made the changes and brought Ryan on one of the fans behind me kept on shouting out I didn't know what I was doing so I'd like to go and try and see him now."