[1] Uehara won the 2013 ALCS MVP Award, and closed the final game of the 2013 World Series against the St. Louis Cardinals.

However, many other teams, including the Yankees, Dodgers, Red Sox, Mets, and Orioles, had shown interest in bidding for Uehara if he were to become available.

[citation needed] In the final game of the 1999 season against the Yakult Swallows, with the league standings already decided, Uehara was ordered to intentionally walk the Swallows' Roberto Petagine in order to give the Giants' Hideki Matsui a chance to catch Petagine for the home run title.

The competitive Uehara complied with the order but showed his bitterness on the mound, kicking the dirt repeatedly and even shedding tears after the third intentional walk.

[citation needed] Uehara asserted his preference in public to be transferred to a Major League Baseball team through the posting system.

Matters would get worse in the postseason when he gave up three home runs in 1+1⁄3 innings to compile a 33.75 ERA before being left off the roster for the World Series due to his ineffectiveness.

[8] Uehara transitioned his role from setup man to closer after season-ending injuries to Andrew Bailey and Joel Hanrahan.

[10][11] Uehara finished the regular season with a 1.09 ERA, 21 saves, a 2.08 xFIP, and struck out 38.1% of batters he faced.

In Game 4 of the World Series, Uehara picked off St. Louis Cardinals pinch runner Kolten Wong for the last out of a 4–2 Red Sox win.

(The next year Greg Holland matched his record for saves in the playoffs, tying John Wetteland, Robb Nen, Troy Percival, and Brad Lidge.

During Boston's post-win celebrations on the field, David Ortiz playfully lifted Uehara over his shoulder after games five and six.

[15] On July 9, 2014, Uehara was named to his first career All-Star Game, replacing injured New York Yankees pitcher Masahiro Tanaka.

[17] Uehara returned to the closer position in the 2015 season, but on August 7, he suffered a season-ending injury when a batted ball struck his right wrist.

He would prematurely end his 2015 campaign with a 2–4 record added by a 2.23 ERA, 47 strikeouts in 40+1⁄3 innings, and 25 saves in 27 attempts as the Red Sox failed to reach the .500 mark for the 2nd season in a row.

[18] In 2016, Uehara finished the regular season with a 2–3 record, a 3.45 ERA, 63 strikeouts in 47 innings, and 7 saves after spending some time on the disabled list with a pectoral strain.

On March 9, 2018, Uehara signed a one-year contract[21] with the Yomiuri Giants, returning to Japan for the first time since 2008.

[23] On July 20, 2018, Uehara became the second pitcher in history to have 100 wins, 100 holds, and 100 saves combined between NPB and MLB.

[30] In the World Baseball Classic, Japan beat Cuba to win the championship; Uehara led the tournament with 16 strikeouts.

During his MLB career, Uehara lived with his family in Baltimore, where he said there were better educational opportunities for his son, Kazuma.