Cox came out to argue after Gorman called Braves shortstop Yunel Escobar out for runner's interference, running out of the baseline on his way to first.
With one out in the fourth inning and Adam LaRoche on first, Escobar laced a 2-2 pitch back up the middle. The ball hit Reds pitcher Bronson Arroyo's back and rolled toward the plate. Arroyo hobbled after the ball and threw toward first, but the throw hit Escobar in the back. Gorman immediately signaled dead ball and called the Atlanta shortstop out.
Replays showed Escobar was running in fair territory, outside the 45-foot-long runner's path in foul territory, when he was hit by the throw. He had to leave the game with a right ankle sprain.
"Unbelievable. His foot was going to hit the bag when the ball hit him," said Cox. "He was inside the line going down there, but when you're on your last stride, you're hitting the bag with the stride, you can only be where you are. I understand what they say running inside, and the guy threw the ball from the foul line so the ball had to hit him no matter where he was."
"I was talking to the home-plate umpire after it happened," said catcher Brian McCann afterward. "First base is in fair territory. It's one of the dumbest rules. If first base is in fair territory, how can you run down in foul territory? It's frustrating. I guess it's in the rulebook and he felt it necessary to call it."
The play was especially frustrating for Cox and the Braves, as a non-call on a similar play cost the team a win earlier in the season.
Cox has now been ejected seven times in 2009.
Jon Cooper is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.