Matsui cut a live batting practice session short Thursday due to left groin tightness, Kevin Acee of the San Diego Union-Tribune reports.
Matsui is now questionable to participate in the World Baseball Classic for Team Japan, though he could resume playing catch as soon as Saturday. The left-hander has been a solid contributor in his first two regular seasons with the Padres, posting a 3.86 ERA and 130:60 K:BB over 126 innings.