Rodriguez, out since April 20 with a strained left groin, threw 80 pitches Saturday. That was 20 more than he did in a similar session Monday.
"He looked pretty good today," manager Cecil Cooper said. "There weren't many balls hit hard, so that's a good sign."
Rodriguez is expected to throw a light bullpen session Monday, then will be set to make the first of two scheduled starts for Double-A Corpus Christi on Thursday.
If there are no setbacks, Rodriguez could return to the Astros rotation when they play a three-game series in Milwaukee May 30-June 1. Rodriguez was 1-0 with a 2.31 ERA in his first four starts before getting hurt.