SAN FRANCISCO — Even with a roster devoid of major leaguers and a mere six months to prepare his club, Japan manager Koji Yamamoto still felt immense pressure to continue his country’s dominance in the World Baseball Classic.

This time, under far different circumstances four years later, two-time reigning champion Japan couldn’t pull off a remarkable three-peat.

Yamamoto took it personally. How could he not on a night Japan lost 3-1 to Puerto Rico after the tournament honored the WBC’s two previous winning managers from his homeland?

“Of course I have aimed for three consecutive winning championships, and I had some expectation that we would be able to do that,” the 66-year-old skipper said. “But this is such a big international game, and it’s been a while since I did the big international game. I did have pressure that I need to do this. However, this was a great experience being as old as I am. I was able to really feel the challenge of the match and being able to face this kind of challenge, it was really exciting.”

Unlike the two previous WBC winners from Japan, this team lacked international star power without the likes of Ichiro Suzuki, Daisuke Matsuzaka and Yu Darvish.

“We were all domestic players from Nippon baseball,” Yamamoto said. “It’s challenging to get adjusted before the season, so as a team, despite the challenges, they really had the unity to fight the game.”

Hirokazu Ibata drove in the team’s lone run with an eighth-inning single against Randy Fontanez, but Japan missed a chance with a costly baserunning blunder — a botched double-steal attempt. It also had the tying run at the plate in the ninth but Fernando Cabrera closed out the win.

The surprising Puerto Ricans first eliminated the star-studded United States, then took care of two-time World Baseball Classic champion Japan two days later in the event’s first semifinal.

Now, Puerto Rico needs one more win to be WBC champion..

“We totally showed we can be the new team, the champion nobody expected,” said Angel Pagan, center fielder for the World Series champion San Francisco Giants. “It means a lot, but not everything, because we’re still missing one more win.”

Alex Rios hit a two-run homer, Mike Aviles singled twice and drove in the game’s first run, and Puerto Rico reached its first WBC final with a big assist from the bullpen.

Relievers Jose De La Torre and Xavier Cedeno each worked out of jams while pitching key moments after winning pitcher Mario Santiago left in the fifth inning with a forearm injury.