General manager David Stearns and manager Craig Counsell met before the game and decided not to start Lucroy.
"He's progressing on something," Counsell said of Stearns. "We thought it best that [Lucroy] not be in the lineup today.
A two-time All-Star, Lucroy is batting .300 with 13 homers and 50 RBIs. He has a $4 million salary this year as part of a contract that includes a $5.25 million team option for 2017.
"He has not been traded," Counsell said. "He's available to us today. I'll use him if something comes up and I have to use him. But [Stearns is] making progress, so we thought it best to not play him."
Lucroy, 30, was in the clubhouse and dressed for batting practice.
"I'm not playing today," he said. "I'm sure it has something to do with things that are going on."