Estrada's throwing session pushed back

PHOENIX -- Brewers right-hander Marco Estrada tweaked his back and will not throw live batting practice Saturday at Chase Field as the club originally had hoped.

Still rehabbing from a strained left hamstring that has sidelined him since June 4, Estrada said he woke up and his back "locked up." The Brewers will be cautious with Estrada moving forward and make him work another side session before scheduling him to face live hitters.

"As far as I know, he needs to throw another bullpen then progress to what we thought he was going to do, throwing to some batters," Brewers manager Ron Roenicke said.

In 12 starts for Milwaukee this season, Estrada is 4-4 with a 5.32 ERA.