It is being reported that Antonio Valencia injured himself when fouled by Glen Johnson, thus winning the penalty kick that ultimately decided their match with Liverpool.
SBNation's Manchester United blog, The Busby Babe, is reporting that Valencia has been seen on crutches. This seems to be a similar injury "sighting" as last week's "Kyle Naughton seen in a boot" news, and while Naughton was thought to have a chance to play last weekend - he didn't.
More information as we get it.