Why the switch?
Pierzynski is 9-for-22 lifetime (.409) against Mark Buehrle, his longtime batterymate with the White Sox.
"He's had quite a bit of success against Buehrle and in a stretch where we're trying to generate as much offense as possible," Farrell said. "That's where we are in the lineup today."
Of late, Ross has struggled mightily at the plate, providing just three hits in his last 27 at-bats.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.