Hernandez last played on June 9 and has missed the Phillies' past 31 games because of a left oblique strain.
The leadoff hitter was batting .277 with five home runs and is tied with Altherr for the Phillies' team lead with 40 runs scored this season.
Altherr suffered his injury Friday night and has missed the Phillies' past two games. He leads the Phillies in batting average (.288) and on-base percentage (.359). He also has 14 home runs and 44 RBIs.