Arsene Wenger was disappointed that Arsenal failed to create many chances in their 1-1 draw against battling Southampton at St Mary's.
Gaston Ramirez opened the scoring for Saints while the Gunners levelled matters shortly before half-time when Guly turned Theo Walcott's free-kick into his own net.
This result and performance was in sharp contrast to Arsenal's 7-3 triumph over Newcastle three days ago.
The hosts more than held their own, particularly in the second half, and Wenger was frank in his assessment.
He said: "We were not very good offensively, we didn't create enough.
"Defensively, we were not too many times under threat but we didn't create enough chances.
"Considering our performance and the result of the game, I don't think we deserved anymore today.
"It is two points lost if you look at the overall target we had for Christmas. It is frustrating and disappointing as we didn't create a lot today.
"Our game lacked purpose, penetration and speed, all qualities we have usually but we didn't see that tonight.
"Maybe we thought we scored seven against Newcastle, we thought we would score again today.
"I felt that we lacked purpose in our game and it was more mental than physical.
"We prepared normally, we prepared well, and Southampton deserved some credit.
"They fought for every ball and were on their toes. They were fighting until the last second for every single ball.
"We did not have enough quality to take them out of position and take advantage of that."
Chris Wilder's side made it three wins in a row and stretched their unbeaten run to 10 games thanks to a narrow victory sealed by Peter Leven's 16th-minute spot-kick.
Referee Fred Graham awarded the penalty after Tom Craddock had his heels clipped by Sido Jombati as he raced into the box.
Yet Yates said: "The ref never gave any free-kicks all game and then gave them a penalty that never was. I've seen the game back and it was never a foul.
"It gave Oxford something to hang on to and they were able to play on the break in the second half.
"I thought we were the better team. It was a stupid goal that we gifted them.
"I thought we had a few chances in the second half but our finishing was a bit disappointing."
Yates added: "It was a toughly contested game on a difficult, tacky pitch with no real quality on view from either side.
"I was pleased with the attitude of my team. We were more committed and more professional than we were against Rochdale (in a 4-1 defeat).
"We did okay but neither team played with much fluency. We've lost, we've got to move on quickly."
