But how often does it happen? He'll throw the ball away once every blue moon. The guy is as lights out at defense as you can be.
I looked at the "Advanced Fielding" stats available at Baseball-reference.com.
Ryan makes no errors on catching throws and relatively few fielding errors. He's made only 33 fielding errors in his career.
However, in the same time, he has made 80 (eighty) throwing errors. I couldn't find any other 3B who had a similarly lopsided split. Beltre's numbers are 131 fielding and 108 throwing (over a longer time), Wright is 78 and 78. Rolen is 140 and 45. Zimmerman already has 35 more throwing errors than Rolen had in his entire career.