Altherr is returning from a right hamstring injury earlier than expected. Assistant general manager Scott Proefrock had said July 19 that Altherr was expected to miss three to four weeks.
Nava is going on the disabled list with a left hamstring strain. He suffered the injury on Friday night and had missed the Phillies' past four games.
Altherr led the Phillies in batting average (.288) and on-base percentage (.359) at the time of his injury. He also has 14 home runs and 44 RBIs.
The left-hand-hitting Nava is batting .303 with three home runs and 17 RBIs this season.