On Tuesday, infielder Henry Rodriguez was recalled from Triple-A Louisville.
The Reds had no comment about Phillips, except an e-mail that read: "Brandon Phillips is away from the team on a private personal matter."
In 71 games this season, Phillips is batting .265 with 11 home runs, and his 60 RBIs rank second in the National League.
Since returning from missing four games with a bruised left forearm sustained when he was hit by a pitch, Phillips is batting .169 (12-for-71) in 17 games.
This is the second callup this season for Rodriguez, who was for 0-for-2 in two pinch-hitting appearances from June 7-10.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.