Jarrod Saltalamacchia, Koji UeharaThe Red Sox knew they were getting a valuable major league arm when they signed Koji Uehara this past winter. But did they really know they were going to get this?

The veteran right-hander has been one of the most important Red Sox this season in a year where the Sox have gone from the laughingstock of baseball to holding a four-game lead in the American League East on Aug. 14. That’s been in large part due to Uehara, who has been invaluable in whatever role he’s taken for the Boston bullpen.

Early in the year, when the pen was a strength of the Red Sox, Uehara was mowing batters down in a setup role. With Andrew Bailey‘s injuries and inconsistencies as well as Joel Hanrahan‘s season-ending injury, Uehara was called on to serve in a different role. He’s been the Boston closer since June 26, and over that time period, he’s been the club’s most consistent closer since Jonathan Papelbon.

The numbers certainly speak for themselves since Uehara took over the closer’s role. ESPN’s John Buccigross tweeted some of the Japanese right-hander’s dominant stats Wednesday morning, and they are eye-popping. [tweet https://twitter.com/Buccigross/status/367605094596222976 align=’center’]

Those numbers are pretty spiffy, to say the least. Using that tweet as the jumping-off point, it’s worth digging even deeper to see how dominant Uehara has been since taking over the role.

  • Following his appearance Tuesday night in Toronto — where he pitched 1 1/3 scoreless innings and picked up the win — Uehara has now pitched 24 2/3 innings since June 16. Of those 24 2/3 innings, he’s thrown 17 clean 1-2-3 innings.
  • Uehara has faced 84 batters in that stretch, and he has 33 strikeouts. He’s walked just two batters.
  • He’s thrown 329 pitches; 74 percent of them have been strikes, getting a swing and a miss 19 percent of the time. Or to put it another way, one out of every five pitches from Uehara is a swing and a miss.
  • He’s allowing 3.3 hits per nine innings pitched.
  • Uehara is averaging 12 strikeouts per nine innings pitched.
  • He’s allowed just one home run.
  • The Red Sox are 20-3 in games he’s pitched over that stretch (26-16 overall), and the club is 42-13 in games he’s appeared in this season.
  • Much was made about Uehara’s ability to throw in back-to-back games on back-to-back days. He’s done so five times since June 26, and he’s pitched a total of 4 1/3 innings over that time, giving up an unearned run on just three hits. He has six strikeouts in that time.
  • In fact, Uehara has pitched 12 times with no days of rest over the course of the entire season. In those appearances, he’s worked 11 innings with a 0.00 ERA. He’s faced 43 batters and has struck out 17 of them, allowing just six hits.
  • Combining his appearances with one day’s rest and no day’s rest for the entire season, he’s worked 32 2/3 innings, allowing just three earned runs for an ERA of 0.83. He has struck out 40 percent of the batters he’s faced in those appearances.
  • He’s given a bunch of high fives, which is still kind of his thing.

Perhaps the most impressive number about Uehara, however, is 4.25 million — in that he’s making $4.25 million this year while turning into a very reliable closer (he also just reached a vesting option for 2014 at the same figure with a chance to push that number to $5 million). There’s still a long way to go, though. He’s never thrown more than 66 2/3 innings in a season, and he’s now sitting at 54 2/3 midway through August. He’s going to be tested — in high-pressure situations with high-pressure pitches — like he never has before, and that’s even before potentially pitching in the playoffs.

However, if Uehara can continue to perform anything like he has since taking over as closer, Boston will enter the stretch drive and maybe the postseason with a very reliable arm in the back of its bullpen.