The Frenchman scored twice after Alvaro Negredo's early opener to make it seven straight wins at home and although it was an impressive display, Nasri insists their form away from home has to improve in order to become a genuine title threat.
"Everything is fine at the moment," he told Sky Sports.
"We had a tough first half today but we came back with the best intention in the second half and scored more goals and kept a clean sheet."
He added: "We have to improve our form away from home and we have the games coming up to do it.
"I think six points is not a lot especially if we can close that gap before we play Arsenal.
"We are coming into an important time and Sir Alex Ferguson always said that if you are up there on Boxing Day then you can be there at the end of the season.
"It's important we respond because we have a lot of games in between at home and away."
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