What is the best age to start playing tennis?

This is a common question that many parents asked coaches, because they want their children to be a success. They want their children to become a professional tennis player so they want to know the perfect age to get start with tennis.
There are many opinions about this topic, I choose two articles about it; the first one is in Hebrew and the second one is in English.

Here is the links for the articles:
Hebrew-

http://www.reader.co.il/article/13126/טניס-לגיל-הרך-באיזה-גיל-כדאי-להתחיל

English-
http://www.syl.com/hb/startplayingtennis.html


The both articles says that no matter what age the child start to play tennis, the most important part as a parent is to make sure that the child having fun by playing!.
The first article says that the right age is between 4 to 6 years old. The second one says that the child needs to be at least 3 years old but they recommend on age four. They also says that age four can be most of the time to early for the child so when the child is five years old can be better. The last thing they think is that by the age of seven the child is for sure ready to start playing tennis.