Quote:

So if the Colts had kept the ball instead of fumbling it, the Saints would have been in quite a predicament, if I understand it correct?



Correct. An onside kick is usually reserved for the final minutes of a game or when the kicking teams defense has shown true dominance over the receiving teams offense. It's a high risk, low percentage play. The clarification a couple posts up about the ten yard rule is correct- the ball isn't live until it's travelled 10 yds OR is touched within that 10 yd distance by the receiving team. In other words, had the ball only gone 5 yds, it could have laid on the field for 5 minutes, until someone covered it. Had the kicking team covered it- still Colts ball.