The England international has notched seven goals in the league this season but says he has to improve his performances with United set to face Newcastle, West Brom and Wigan over a busy festive period.
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"I could feel it on the pitch that things weren't right at Swansea," Rooney told the Daily Mail.
"Some days you have an off day I could feel that and I couldn't complain at being substituted.
"But the good thing I think about football, and especially over the Christmas period, is that you have lots of games and the Swansea game has gone for me and it is certainly not one I will remember."
The Red Devils were top of the table for Christmas with a four-point lead over rivals Manchester City but the 27-year-old is confident that they can continue to increase the gap.
"The position we are in at the minute, it is a great opportunity to make that gap even bigger between us and Manchester City at the top of the league," he continued.
"Obviously against Swansea we couldn't do it but, as I say, hopefully we will get six points from the next two games and see what happens."