In slow motion, the play appeared to be a lot closer than initially expected. But after a review in New York, the play was ruled as stands in the Rockies' 3-0 win at Coors Field.
Even with Blackmon's good jump, Rivera's throw appeared to get there in plenty of time for Yangervis Solarte to lay down a tag.
Seeing as that was the third out of the inning, manager Walt Weiss decided to take his chances with a challenge.
Before running into an out on the basepaths, Blackmon gave the Rockies a 2-0 lead with an RBI single to right.
Cody Ulm is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.