The England international admits the Gunners were "not up to scratch" at Anfield but insists they have an opportunity to put things right when they face David Moyes' men
Arsene Wenger's side slipped a point behind Chelsea at the top of the Premier League after a 5-1 hammering at Anfield on Saturday, which emphatically ended their eight-game unbeaten run in the top flight.
The Emirates Stadium outfit were 4-0 down after only 20 minutes, as Raheem Sterling and Daniel Sturridge added to Martin Skrtel's early brace in an electrifying start by the Merseysiders.
That game marked the beginning of a tough sequence of fixtures for Arsenal, which includes an FA Cup fifth-round clash with Liverpool on Saturday before their Champions League last-16 tie against holders Bayern Munich.
First up is a Premier League meeting with United on Wednesday, though, and Oxlade-Chamberlain feels it is Arsenal's "responsibility" to react from their chastening defeat at Anfield against the reigning champions.
"We are very disappointed, especially with the first half," the England international said. "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 a great opportunity on Wednesday night.
"When the first goal went in early 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 we did that. So there are some mental positives today but we have to put it right on Wednesday."