Santos (lat) threw a 30-pitch up-and-down bullpen session Saturday, Daniel Kramer of MLB.com reports.
Santos tossed 15 pitches in both of his sets and mixed in all of his pitches. Assuming Santos comes out of the side session without any renewed discomfort in his right lat, he'll likely be cleared to face hitters in a live batting practice session later this week. The Mariners remain optimistic that Santos will return from the 60-day injured list and make his team debut at some point in July.