"He's feeling much better today," Black said.
Alonso had an injection in the knee on Saturday night to reduce some of the soreness. Doctors said Alonso would need 48-72 hours to feel healthy.
The 25-year-old rookie is batting .254/.325/.345 with two homers and 18 RBIs.
Jesus Guzman started at first base on Monday and batted fifth against Astros left-hander Wandy Rodriguez. Guzman entered the game batting .236 with one homer and 24 RBIs.