Cano left the game, and X-rays revealed a non-displaced fracture. The injury will not require a cast or treatment, just rest. Mariners trainer Rick Griffin spoke with Cano, who reported no pain.
Cano, 32, is coming off his fifth consecutive All-Star season, which saw him bat .314 with 14 home runs in his first year as a Mariner. He was one of the highest-profile players on MLB's All-Star Series tour of Japan, regularly starting at second base and batting second for John Farrell's team. Cano ended up going 2-for-10 in three games.
In Cano's absence, Astros second baseman Jose Altuve -- who has come off the bench for most of the Japan Series -- should see the bulk of playing time at the position.
Historically one of the league's most durable players, Cano has averaged 160 games per year since 2007. He signed a 10-year, $240 million contract with the Mariners last winter after spending the first nine seasons of his career with the Yankees.
The Japan All-Star Series wraps up with one more game at the Tokyo Dome on Sunday, followed by Game 5 of the series Tuesday in Sapporo. The MLB All-Stars will then travel to Okinawa for one final exhibition game, which does not count in the Series standings.
"It's part of the game, getting hurt," Cano said before leaving the Tokyo Dome and learning of his fracture. "I'll be fine."
Japan All-Star Series schedule
• Exhibition: MLB 8, Hanshin-Yomiuri 7 | Box
• Game No. 1: Japan 2, MLB 0 | Box
• Game No. 2: Japan 8, MLB 4 | Box
• Game No. 3: Japan 4, MLB 0 | Box
• Sunday: Game No. 4 at Tokyo Dome, Tokyo (6 p.m. JT/4 a.m. ET)
• Monday: Travel day
• Tuesday, Nov. 18: Game No. 5 at Sapporo Dome, Sapporo (7 p.m. JT/5 a.m. ET)
• Wednesday, Nov. 19: Travel day
• Thursday, Nov. 20: Exhibition game vs. Samurai Japan, Okinawa Cellular Stadium, Okinawa (6 p.m. JT/4 a.m. ET)
MLB Network will broadcast all seven games of the Japan All-Star Series, and MLB.TV subscribers in the U.S. and around the world can watch live and on-demand streams of every game as well.