The Gunners lost top spot in the Barclays Premier League after a 5-1 hammering by fourth-placed Liverpool, who blitzed their visitors with four unanswered goals in the opening 20 minutes.
Arsene Wenger's side have slipped to second, a point behind Chelsea, but host Manchester United on Wednesday looking to recover both lost ground and pride.
"We are very disappointed, especially with the first half," Oxlade-Chamberlain told arsenal.com.
"We know we are better than that so in that sense we are gutted.
"But these things happen in football and it is our responsibility to turn that around and we have great opportunity on Wednesday night.
"When the first goal went early (in the first minute) you have to respond and 'see out' the next 10 or 15 minutes.
"We failed to do that and, credit to Liverpool, I thought they were brilliant and we were not up to scratch.
"In the second half we knew we had to improve and I believe that we did that.
"So there are some mental positives but we have to put it right on Wednesday."
Defender Martin Skrtel scored from two set-pieces before Raheem Sterling and Daniel Sturridge put the game out of sight well before half-time.
Sterling added a second just after the break before Mikel Arteta scored a consolation for Arsenal after Steven Gerrard brought down Oxlade-Chamberlain in the penalty area.
Gunners boss Arsene Wenger admits his side have put themselves under pressure with the performance as their title credentials are now being doubted.
"It raises questions that we have to answer on Wednesday night," said the Frenchman.
"But it is not what people say it is how we respond what matters.
"People of course raise questions but we have only one way to answer that and it is on Wednesday night."
Asked whether they were still title contenders Wenger added: "Of course, because no matter what happens it will be mathematically possible.
"It is always what you make of a defeat which decides your future and we have a lot to answer for and a lot of answers to find.
"It was similar situation after Manchester City (where they lost 6-3 in December).
"It was a Saturday 12.45pm kick off and we similarly conceded early goals.
"We have to analyse well what happened and why it happened but we didn't look sharp physically as well."
After the City defeat, Arsenal went on an eight-match unbeaten run which saw them garner 20 points, and Wenger sees no reason why they cannot repeat the feat.
"If we do that in the next few games that will be okay," he said.
"We are very disappointed but we will not lose our confidence and belief that we can still do it."