What Could Cause Loss Of Control While Trying To Stand Up?

I have noticed that when playing rugby league on the week end that in the first two tackles of the match as i went to get up off the ground i had a lack of balance and control trying to stand up. I was not hit hard and did not suffer in any way during the tackles. I continued on with no more affects. I was well hydrated and had plenty of sugar on board. I am a 43 male. I would consider myself in fair condition after loosing 70kg over the past 3 years. I currently weigh in at 120kg.