DENVER -- In one of the more bizarre plays you'll ever see on a diamond, Phillies second baseman Cesar Hernandez reached second base safely on an attempted double play that went awry in the fourth inning of Sunday's 4-1 loss to the Rockies, then began walking off the bag and was tagged out.

Hernandez was on first after reaching on an error, and Rhys Hoskins hit a ground ball to shortstop, where Trevor Story scooped it up and threw to Garrett Hampson at second base to start what could have been an inning-ending 6-4-3 double play. But Hampson dropped the ball in the process of trying to turn the double play.

Hernandez thought second-base umpire Joe West had called him out, and he began walking back to the Phillies' dugout. When he realized that he wasn't out, Hernandez got into a rundown that ended in a 6-5-4 putout.

"It is ultimately my fault," Hernandez said through an interpreter. "I should've known better. I should've stayed on the base until it was 100 percent sure if I was out or I was safe. I just assumed I was out."

Hernandez said he didn't see the ball fall out of Hampson's glove or hear West say he was safe, but he nevertheless should have looked to see West's hand signal.

"Sometimes what you try to do when you're stealing a base is, you put your head down to protect your face, and that's what happened," Hernandez said. "But again, that's not really an excuse. ... It's a learning experience for me, and hopefully it won't happen again."

It was a mental mistake on Hernandez's part, and also the second error of the inning for Hampson, who was unable to backhand Hernandez's ground ball to open the frame.

Rockies starter Jon Gray was able to escape the jam, allowing a double to Maikel Franco but getting Roman Quinn to fly out to end the threat and strand Hoskins at third.