Yes, use the leave color effect, but keep in mind that this effect is very limited. If you have after effects you can use it to get much more precise with mask to getter better results. Premiere's leave color may be work perfectly for what you are trying to do, just depends on the footage quality and contrasting color in the ball.
In the Effects Panel, there's a little question text box. If you type in "black" by then you'll be taken to Video Effects (ignore the Video Transitions that will also be listed) and you'll see Image Control>Black & White. That little text box allows you to distill your view of the Panel to just what you're looking for.
[Edit] Tip: not sure how you wish to introduce this Effect, but if you want to ease into it, you cannot Keyframe it, like many others. However, you can use the Razor to "cut" your Clip into, say three sections. Apply this Effect to the middle and then add a Cross-Dissolve to the two "cuts."
[Edit 2] You did say how you wished to use this and I missed it - duh! With a dupe of your Clip, you can use my suggestion above, and then apply a Track Matte Keying effect with a Track Matte to kill the B&W Effect on the original Clip. This Matte can be Keyframed to follow any motion. Sorry that I missed that last part.