With the Dodgers leading, 5-0, Chien-Ming Wang on the mound and two outs, Matt Kemp ended up scoring the sixth run on a fielder's choice by Hanley Ramirez.
On the replay, third baseman Ryan Zimmerman tagged Adrian Gonzalez before Kemp touched home plate, but Porter ruled that Kemp had already scored before the out was made.
That turned out to be a huge play in the game because the Nationals lost on a homer by Kemp in the top of the ninth inning after they rallied for six runs to tie it in the eighth.
Porter was not available for comment, but knew he made a bad call, according to Johnson. Porter apologized an inning later. Johnson said Porter thought the bases were loaded when there were actually runners on second and third. Porter then went to his fellow umpires to help him with the call.
"Alan said, 'I messed it up.' ... [The umpires] are good guys. I don't have a beef with them," Johnson said. "It's just sometimes when you miss one, you get help. He got help and they still didn't get it right. He just thought about the situation and then realized he wasn't thinking along those lines."