"I'm done. It's a simple decision," LaRue told the St. Louis Post-Dispatch.
During the brawl at the Great American Ball Park, Cincinnati's Johnny Cueto repeatedly kicked LaRue in the head with his spikes. LaRue was placed in the disabled list and Cueto was suspended for seven games.
"When it first happened I thought it was just another concussion. I felt within a couple days I would be fine," La Rue said. "But I didn't feel good. And for a long time nothing progressed."
The 36-year-old spent eight seasons with the Reds and has been on St. Louis for three years.