MINNEAPOLIS -- Nationals right-hander Garrett Mock is the leading candidate to replace left-hander Odalis Perez in the rotation this weekend against the Rangers. Mock has a 4-2 record and a 3.12 ERA with Triple-A Columbus.

The last time Mock pitched in the big leagues was on June 8 against the Giants. It was his Major League debut and it was an outing he would like to forget. He didn't get past the fifth inning as the Nationals lost to the Giants, 6-3, at Nationals Park.

A far as Perez goes, he had a bullpen session on Monday and didn't feel any pain in his left shoulder. He threw 35 pitches, mostly fastballs and changeups. He will have another bullpen session on Wednesday. Perez is eligible to come off the disabled list on June 26. He hasn't pitched since early June because of tendinitis in the shoulder.