With three off days between now and May 6, the Pirates can get Archer some time to heal without needing a fifth starter. The Pirates recalled right-hander Michael Feliz on Saturday.
Manager Clint Hurdle said Archer felt the thumb issue last weekend against San Francisco and again Friday night, when he gave up six runs over four innings in a loss to the Los Angeles Dodgers. Archer is 1-2 with 4.33 ERA in five starts this season.
Pirates director of sports medicine Todd Tomczyk said that Archer's injury resulted from wear and tear.
Tomczyk said outfielder Corey Dickerson would not begin his expected injury rehabilitation assignment because he experienced tightness in his injured shoulder while throwing from 110 feet. Dickerson will meet the club at Texas next week and be examined.
Outfielder Lonnie Chisenhall, on a rehab assignment after breaking his right index finger, felt left calf tightness while running the bases Friday. He will return to Pittsburgh to be examined.