With Boston's roster in a total state of flux -- thanks to a combination of injuries and lack of performance -- the Red Sox summoned Tazawa to the Majors Leagues and activated him for Friday night's game against the New York Yankees.
It was an exciting moment for the 23-year-old right-hander, who had never pitched in professional baseball until this season.
"I found out last night," Tazawa told Japanese reporters. "I wasn't sure. I said, 'Really?' They said, 'It's real.' I was ready to pitch tomorrow's Futures At Fenway, so this was a surprise. I only pitched two times at Triple-A. I'm very happy. I'm a little nervous and a little happy."
Boston's international scouting department found Tazawa while scouting the industrial leagues in Japan. The Red Sox were impressed enough to sign him to a Major League contract (three years, $3.3 million) in December.
There's a chance Tazawa will start for the Red Sox on Tuesday night and fill the rotation slot vacated by John Smoltz, who was designated for assignment. It depends on whether -- or how much -- Tazawa is needed out of the bullpen during the Yankees series this weekend.
Tazawa spent much of Spring Training with the Red Sox and turned in some impressive performances.
"I caught him on the side," said Red Sox catcher Jason Varitek. "I can't remember how much I caught him in the game. He had very fundamental, very good mechanics and he has some good stuff to go with it."
Did Varitek think Tazawa would be in the Major Leagues this season?
"Yeah, but there's some youth there, too," Varitek said. "Stuff-wise, yeah."
Tazawa went 9-7 with a 2.55 ERA in 20 starts in the Minor Leagues, 18 of which were for Double-A Portland.
The Red Sox projected that Tazawa would join the Major League team in September, when rosters were expanded, but circumstances dictated otherwise.
"Everyone's development path is different," said Red Sox general manager Theo Epstein. "This guy showed up in Spring Training and was mature well beyond his years from a baseball standpoint and from a personal standpoint. Certainly, he pitched extremely well at Double-A. He had just gotten his feet wet the last couple of weeks at Pawtucket.
"Perhaps, in a perfect world, he would have had a little time at Pawtucket, but I also think he's ready. I also think he's ready to contribute up here. He's lived up to the scouting reports we got on him from Craig Shipley and our international staff, and I think he's ready to contribute at this level now."
Is Tazawa on the roster temporarily or for the rest of the season?
"We'll see," said Epstein. "Given everything that is going on with the club right now, I don't think it's possible to make any definitive statements. Because we're at a critical juncture at a challenging time and so many things have gone not as anticipated the last couple of weeks, we're certainly day to day with a lot of things, if not inning to inning and pitch to pitch."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.