If you are a league follower, know the stats, who is in form etc, this not a gambling!
Gambling is when you play roulette and anything can happen.
But I am of the view that whenever you bet money in any place in any game or any thing then it is gambling. We call an action as gambling when two or more persons put some money on a thing happening or game and one of them win them all and the remaining lose according to the rule. So in that definition betting on sports is also gambling.