Lopez accompanied the Cardinals to Pittsburgh to begin a three-game series, but was told before Tuesday's game by manager Tony La Russa and general manager John Mozeliak that he was being let go.
"He's healthy. He's just not going to get starts and not going to come off the bench," La Russa said. "He was told and he said, 'OK.' There was no reason for him to be around, so ..."
Mozeliak said Lopez arrived late at the stadium for Monday's game at Florida, a makeup of a previous rainout.
"He was late, and it was not the first time," Mozeliak said. "When you think about what we're trying to accomplish here, we brought up a lot of young players with our September callups, and we wanted to make sure they understand the message we want heard. It really came down to a tipping point and it was either just not play him or allow him to go home."
Lopez's lateness was beginning to wear on the team's staff, especially with the Cardinals fighting the perception that some players have already given up on the season.
The Cardinals are nearing elimination by Cincinnati in an NL Central race they led as late as Aug. 14.
"It was one thing, I think, the coaching staff had been very tolerant of, and they came to a point where they'd had enough," Mozeliak said. "Obviously with two weeks left in the season you would prefer not to have to make these kind of decisions or react in this way, but I understand why we did it. I think it really sends a strong message to the younger players on what our expectations are."
Lopez, signed during the offseason as a utility player, hit .231 with seven homers and 36 RBIs in 109 games, making 89 starts. He filled in for two months as the starting third baseman when David Freese was hurt, but his playing time was cut after Pedro Feliz was acquired from Houston on Aug. 19.
Lopez's salary was $1 million, and he already had earned $400,000 in performance bonuses by reaching 400 plate appearances. He had 425 and would have earned an additional $200,000 for reaching 450.
"He's had a tough year," La Russa said. "And I was his biggest advocate."