The Padres placed Matsui (groin) on the 15-day injured list Wednesday.
Since straining his left groin in late February, Matsui has begun throwing off a mound and is slated to face hitters soon, but he'll still likely to remain on the shelf until at least around mid-April. Because he missed the entire Cactus League slate, he'll need to complete a rehab assignment in the minors before making his season debut with the Padres.