Oxford manager Chris Wilder was disappointed with his team's defending in their 3-2 defeat at home to Dagenham.
Sam Williams and Luke Wilkinson capitalised on some slack play from the hosts at set-pieces to score either side of Luke Howell's second-half effort.
But the away side had to hold on after Tom Craddock grabbed his second of the game and Daggers midfielder Kevin Maher was sent off for a second bookable offence with 20 minutes to go.
Speaking after the defeat, Wilder said: "The goals we conceded were awful. If you can't defend two out of three corners...We conceded poor goals and we were always chasing the game.
"We just didn't get going. It was a flat performance. When they went down to 10 men, the quality wasn't there from us. We showed a bit of spirit by fighting back a bit in the second half, but we've not shown a lot of quality on the ball. This was a big week for us with two home games and it's started badly.
"There were five draws in the division (on Tuesday night) and it annoys me that we couldn't get something from the game, a draw at least, which would have kept us in there."