Mullins (quadriceps) took part in the Orioles' batting practice ahead of their matchup with the Astros on Sunday, Taylor Lyons of The Baltimore Sun reports.
Mullins was ruled out of the lineup for the second game in a row due to a quadriceps injury he suffered Friday, but his participation in batting practice is a positive sign. The Orioles have a day off Monday before they launch a three-game series on the road against the Dodgers on Tuesday, and Mullins can be considered day-to-day for the time being.