First, grab the Ellipse Tool (L) and draw a 130 x 130px circle. You can select any fill color for the moment.
With the circle selected, go to Object > Create Gradient Mesh. Select 4 Rowsand 4 Columns then hit OK.
Now, you need to distort a little the mesh lines created. To do so, just select using the Direct Selection Tool (A) the mesh points and move them one by one. Also adjust the handles if needed.
This is what you should get:
Now, use the Direct Selection Tool (A) to select each mesh point and fill them with different shades of gray. This way you will define areas of light and shade on the ball. Follow the color code and after you are done the ball should look like in the next image.
At this point you need a copy of the circle but if you are like me and forgot to keep a copy, use the next trick. Select the mesh-shape then go to Object > Path > Offset Path and apply a 0px Offset. As a result you will get the circle of same size but without the mesh lines. The new circle must be in front of the mesh and you can now fill it with the color indicated and set the Blending Mode to Color. I will call it «color-shape».
You can also try other colors and depending on the color another Blending Mode.