Koji UeharaRed Sox general manager Ben Cherington had a busy offseason revamping the Red Sox roster after a miserable 2012 campaign, bringing in players like Mike Napoli, Ryan Dempster, Shane Victorino and Jonny Gomes. But Cherington’s most valuable addition was perhaps Koji Uehara.

Cherington signed Uehara to a one-year deal with the intention of adding a veteran arm to an already deep bullpen. Little did he know he would be relying on the Japanese sensation to handle the everyday closer duties. With Joel Hanrahan undergoing season-ending Tommy John surgery and Andrew Bailey struggling with inefficiency and health problems, Uehara was thrown into the closer role and took immediate advantage of the opportunity.

The right-hander has posted a dominant 1.43 ERA in 50 1/3 innings of relief work, and he continued his success on the mound with another save in Saturday’s 5-2 win over the Diamondbacks.

“Whether it’s been in the setup role or closer role, he’s been the same guy. He’s been dominant,” manager John Farrell said after the win Saturday. “Tonight, once again he put’s up a zero. He’s having a phenomenal year for us.”

Uehara’s strikeouts are up (12.52 strikeouts per nine innings), walks are down (only eight on the season), and his WHIP of 0.70 ranks among the best in the league. The 38-year-old has been especially dominant as of late, surrendering only three hits and no runs over his last 11 appearances. Uehara has always been known to be a fly ball pitcher who has a tendency to give up the longball, but his pitch control has been so precise that he has only allowed five home runs in his 51 appearances.

Uehara’s impact with the team goes further than his statistics, though. The Red Sox bullpen has been depleted during the 2013 season, with Hanrahan and Andrew Miller both suffering season-ending injuries. Add Bailey’s injury problems to the mix, and many Boston faithful were calling for Cherington to bring in some bullpen help before the trade deadline. Cherington was reluctant, though, instead waiting it out until the last minute.

“The most efficient way to do it is to ignore [the trade market] completely,” Cherington told The Boston Globe after Miller’s injury. “But then you run the risk of not having enough guys out there. We can’t say never to a trade for a reliever just because it’s hard to predict. We have to evaluate each possibility for what it is. If you find something internally, that’s always a better way to go.”

Uehara turned out to be the internal candidate Cherington was looking for, which allowed the general manager to pursue, and ultimately land, starter Jake Peavy in a three-team deal. With ace starter Clay Buchholz caught in disabled list limbo, Cherington’s trade deadline priority was to add that extra starter. He was only allowed that luxury because of Uehara’s consistent pitching, which eliminated a bullpen concern. While the Red Sox could always use more relief, the ninth inning is taken care of.

Even though Uehara didn’t garner enough votes to win the final American League All-Star roster spot, his performance throughout the season is worthy of consideration for the team’s most valuable player.