If you haven't already done so, you may want to read up on my soccer ball tutorial first. Once you have created your soccer you'll learn how to deflate it with this tutorial!
Step one
Using the Pick Tool, select your soccer ball. Then on your toolbox, go to your interactive tools and choose the Interactive Envelope Tool:
Step two
At the top of your screen you'll see there are different options for your Interactive Envelope Tool. We want to choose the Envelope Single Arc Mode:
Step three
You'll see there are 8 handles to choose from. We want to grab the top middle handle:
Step four
Drag downward until you get the following result:
And there you go, a deflated soccer ball! Play around with the different modes and see what else you can come up with.
Alternative method
Another alternative to the interactive tool is the Envelope Docker. To view this, go to Window > Dockers > Envelope. You can use preset shapes as well as other options. Play around with the different settings and let your imagination run wild!
More Vector Graphics: 
