St. Louis catcher Yadier Molina fired the ball to third baseman Matt Carpenter, who slapped the tag on the diving Walker to get the out call from third-base umpire Alan Porter.
After a brief review, the call stood.
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.