Barry Chin/Globe Staff

By almost every statistical measure, Koji Uehara has been the best relief pitcher in the American League.

Stephen Dunn/Getty Images/File 2006

He got his start in college and worked his way to games like the World Baseball Classic in 2006.

Koji Sasahara/AP/File 2002

Former Red Sox outfielder Gabe Kapler played with Uehara for the Yomiuri Giants in 2005.

Koichi Kamoshida/Getty Images/File 2006

"He was the Greg Maddux of Japan, somebody with great control," said Kapler, now an analyst for Fox Sports 1.

Shizuo Kambayashi/AP/File 2002

Barry Bonds held his bat upside down after he was struck out by Uehara during the opening game of the Japan-US all-star baseball series.

Shizuo Kambayashi/AP/File 2002

Those experiences only added to Uehara's desire to play in the majors.

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Uehara came to Major League Baseball when he signed with the Baltimore Orioles.

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"As a teammate, I think he was one of the best teammates I ever had," said Orioles center fielder Adam Jones.

Ronald Martinez/Getty Images/File 2011

Uehara was traded to the Texas Rangers. His wife and son live in Baltimore during the season and often for a few weeks after.

Ronald Martinez/Getty Images/file 2011

When the Red Sox offered him a one-year contract worth $4.25 million, he took it.

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Only in recent weeks have the souvenir stands at Fenway Park sold T-shirts bearing his name and No. 19.

JOHN TLUMACKI/GLOBE STAFF

For now, the only thing that matters to him is continuing this unprecedented run.

Winslow Townson/Getty Images/File 2013

"I can't lose focus on what I'm doing," he said. "I think about the next pitch, the next batter. That's it."