Houston recalled right-hander Collin McHugh from Triple A Oklahoma City, and he is scheduled to start Tuesday against Seattle.
Feldman is 3-1 with a 1.69 ERA in four starts, the last a loss to Kansas City on Thursday during which he gave up five runs - four earned - and nine hits in six innings. Porter said Feldman felt the injury while preparing to throw a bullpen session, and the manager said he hopes Feldman will miss just two turns in the rotation.
''It's obviously unfortunate. He's been our best pitcher all year,'' Porter said. ''But at the same time, I would rather be safe than sorry.''