Doncaster Rovers: Ferguson frustrated at lack of clinical edge in Oxford game his side 'should not have lost'
Rovers had the better of the chances throughout the game and showed some excellent build-up play but failed to transform that into goals.
And they were hit with a second half suckerpunch from Oxford, who scored a counter attack goal through substitute James Henry.
"It was a game we shouldn't have lost," Ferguson said.
"We had the clearer chances in the game. We didn't take those clear chances.
"There weren't many in the game but the ones there were fell to us.
"It was important that we took one before they did.
"We had to deal with that goal better.
"I don't think they troubled us too much.
"In the second half we came on strong and we were the dominant team.
"But we just weren't clinical enough.
"I felt a lot of the stuff we did was good. It was what we wanted and the energy levels were good."
Alfie May, John Marquis and Matty Blair in particular all missed excellent chances to score for Rovers.
Ferguson also felt Rovers should have had two penalties for fouls on Jordan Houghton and May.
He said: "I think we should have had two penalties.
"We've had a look at both of them.
"But we didn't get the decisions and they are key decisions.
"If the one on Jordan Houghton is not a penalty, it's a dive. But he hasn't booked him, so what is it?"