Yomiuri Giants right-hander Koji Uehara was removed from the active roster Friday after suffering a right hamstring injury during a game Thursday.
Team officials said Uehara, who sustained the injury while running on the basepaths, is expected to be sidelined for at least 10 days and miss the early stages of interleague play starting Tuesday.
The 31-year-old left the game against the Hanshin Tigers at Koshien Stadium after allowing two runs and six hits in 4-1/3 innings.
"There is no guarantee that he'll be back after 10 days," said pitching coach Takao Obana, who was cautious after Uehara had the latest recurrence of his chronic injury.
Uehara is the latest injury casualty among the rotation pitchers of Central League leader Yomiuri following the departures of southpaw Hisanori Takahashi and veteran right-hander Masumi Kuwata.
Uehara has a 2-1 record with a 3.38 ERA and a team-high 32 strikeouts in six starts this season. Earlier this year, he helped Japan win the inaugural title at the World Baseball Classic.