Oxford boss Chris Wilder was left to rue his side's poor finishing as the their eight-game unbeaten run came to an end with a 1-0 loss at nine-man Gillingham.
Joe Martin, for two bookings, and Lewis Montrose, who lashed home on the stroke of half-time, were both shown red by referee Gavin Ward for the home team while the visitors missed a glut of chances in both halves.
Wilder said: "Up to the goal, we absolutely dominated them. We controlled every part of that game and had the chances to show for it. But that's where games are decided and yet again we have missed some fantastic opportunities to put us in the lead."
He added: "We had 20 opportunities on goal again but that's the disappointing thing - we just need to be a bit more patient. I think we forced it a bit in the second half even though we created some fantastic chances.
"Their goalkeeper has made some fantastic saves. It is a bit like a broken record and it is a bit disappointing but I know we are on the right track."
Gills boss Andy Hessenthaler said: "I thought we were terrific. It was a siege mentality when things were going against us.
"We made some poor decisions as individuals. It was backs-to-the-wall stuff and hopefully we have opened a few people's eyes. It shows people what spirit we have within the camp and I tell people to wear the shirt with pride, and every single one of them did that.
"We have to start games a bit better. They had a lot of possession without really hurting us. We adjusted at half-time but then we had to readjust again.
"It just shows what a dressing room we have got fighting for each other to get a result and that's what they did.
"The kid [Montrose] gave everything second half and who I am to tell people they can't make challenges - I was the world's worst. It is very difficult for me to crucify the fella - he gave everything and he will learn from it and he has won us the game with the goal."