Anderson, who had his back toward Morgan, didn't have the ball.
The Nationals put the game out of reach during a six-run inning off former Washington closer Mike MacDougal, with Willie Harris' two-run double and Roger Bernadina's two-run homer highlighting the output.
Harris' hit should have been a bases-clearing knock, but third-base umpire Angel Hernandez called Morgan out, because a live baserunner cannot be touched or aided by a teammate or coach. Ivan Rodriguez pushed Morgan back to home plate when Morgan missed the plate while trying to knock Anderson down.
The replay showed there wasn't a need for Morgan to touch Anderson, because the ball wasn't close to the plate.
"It was totally inexcusable," Riggleman said. "It was a mistake. I can't minimize it. If I take the approach that there is nothing wrong it, then we are going to get people hurt on the field. It has never happened before and it will not happen again."
Riggleman believed Morgan wasn't thinking because he was angry that he was hitting eighth in the lineup. Morgan, who was out of the lineup Sunday, usually leads off.
"He was upset about some things and did an unprofessional thing -- he went after the catcher," Riggleman said. "I certainly don't condone that. We have all made mistakes. I don't think that is Nyjer's style of play to do something like that. Maybe he thought I was there with that equipment at the plate. I think [hitting eighth] had a lot to do with it."
Said La Russa, "[Morgan] had a brain cramp. I appreciate the way they handled it. They handled it internally, and they made it clear to us that it was a mistake. The Nats did what they had to do to defuse it. Guys make mistakes. I made it a point not to say anything after the game. I didn't say a word."
Morgan, who said he thought there was going to be a play at the plate, admitted that he was fooled by Albert Pujols' arm fake toward home plate.
"I got fooled by the arm fake and then I saw the catcher get ready to load up," Morgan said. "It looked like he was getting ready to start defending himself. If there is a next time, I guess I will slide. I don't want it to look like I'm trying to hurt somebody."