CHICAGO -- Ryan Zimmerman was dead to rights at home plate, but the umpires wanted to make sure catcher Welington Castillo wasn't blocking the plate.

Zimmerman led off the second inning of Thursday's series opener against the Cubs with a double. Two batters later, he headed for home on Wilson Ramos' ground-ball single to left, and was tagged out at the plate on a perfect relay.

Crew Chief Jerry Layne, working second base, issued a review of the play to make sure that Castillo wasn't in violation of Rule 7.13, which prevents catchers from denying the runner a clean lane to home plate. The call was confirmed after a brief review, denying the Nationals a chance to take a 1-0 lead.