Kinda like seeing this...kids should have childhoods not slugging it out against a ball machine a la Agassi.
at age 13/14 is a good time to start thinking you could dedicate yourself to a sport since by then you will have had a chance to play multiple team sports as a 10-13 year old.
I had a buddy growing up who his Dad had him out Golfing from like age 4. All the time (had a putting green in the back yard) He would take us to the driving range I'd be having fun hitting balls while he would constantly adjust his sons form and be critical of each shot.
He played on our high school team and one easily on of the best players in the area. But he also played Baseball and loved it was on our championship team and went to college with it graduated and now works in some research field.
You couldn't pay him to golf now. But I have got him into Tennis =)