Federer calls medical timeout 'precaution'; del Potro next

NEW YORK (AP) -- The only bit of trouble for Roger Federer in his fourth-round match at the U.S. Open was when he felt the tightening of a muscle at the back of the top of his left leg....

from AP Top Sports News at 11:37 p.m. EDT http://ift.tt/2x5Jx6k