Celtic’s Dylan McGeouch got knocked unconsciousness following a nasty head bump with Real Madrid’s Nuri Sahin during the 2012 Herbalife World Football Challenge. The heads coming together left McGeouch motionless for a while while paramedics attended to him on the pitch.

According to the BBC:

“He is travelling back with us which is great news,” manager Neil Lennon told the club website.
“He needs a plate inserted in his jaw and I think he may made need an extraction of a tooth which has been damaged.
“Thankfully there are no neck or head injuries. It was very similar to the injury Henrik [Larsson] had when he broke his jaw against Livingston that day. So we might be looking at four to six weeks.

H/T The Big lead