Why Does Martin Kaymer Warm-Up With A Tennis Ball Around His Neck?

Far be it from me to question someone who just posted a 63 on a very difficult golf course (Smits game story here), but if you were watching Morning Drive today you saw Martin Kaymer warming up for round two of The Players with a tennis ball tied to a string around his neck.

I repeat, a tennis ball worn like a credential. Around his neck. Whoa Nellie!

Golf Central Doc noticed
the next craze in wacky warm-up techniques back at the Masters and posted this clip.