Hasn't been training between games?
http://www.westlondonsport.com/qpr/ji-sung-park-still6-out-but13-nelsen-overcomes-injury
"Nelsen was also unable to train earlier this week but took part in Friday’s session and is expected play against the Potters."
I think its more to do with them wanting him to be fresh for their crucial game against Southampton, and a suspension to Mbia rather than any risk of aggravating an injury...