The Giants need a starting pitcher with right-hander Matt Cain on the disabled list with an elbow injury.
Escobar and Hembree were pitching with the Giants' Triple A affiliate in Fresno. Escobar, 22, is a left-handed starter Hembree, 25, is a right-handed reliever.
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The St. Louis Cardinals signed free agent veteran catcher A.J. Pierzynski to a contract on Saturday.
Pierzynski was in the Cardinals' lineup against the Chicago Cubs batting sixth and starting behind the plate.
Pierzynski, 37, is with his sixth team in 17 seasons. He was released by the Boston Red Sox 10 days ago. He batted .254 with four home runs in 72 games with the Red Sox.
The Cardinals are in need of a catcher with All-Star Yadier Molina expected to miss eight to 12 weeks with a torn ligament in his right thumb.
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The National Baseball Hall of Fame announced Saturday that it is cutting the number of years that a player can remain eligible for induction from 15 years to 10 years.
That means players including Barry Bonds, Roger Clemens, Mark McGwire and Sammy Sosa will have less time to remain on Hall of Fame ballots.
The Hall of Fame is also installing a new balloting and registration process for Baseball Writers' Association of America voting members. The changes are effective immediately and will reflected voting in 2015.
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The Cleveland Indians recalled right-handed pitcher Zach McAllister from Triple-A Columbus and optioned right-hander Josh Tomlin to Columbus.
McAllister, 26, is 3-5 with a 5.28 ERA in 12 starts with Cleveland.
(Editing by Gene Cherry)