NEW YORK –– Almost exactly eight months after he left the Japanese amateur leagues behind and signed with Boston, Junichi Tazawa is in the American major leagues, and ready to play a significant role on one of the best teams in baseball.

Tazawa was called up Friday afternoon to replace John Smoltz, the future Hall of Famer who flamed out in his Boston tenure. Tazawa will start out in the bullpen, but could move to the starting rotation soon. It’s possible he could make a start Tuesday in place of Smoltz if he isn’t used out of the bullpen in the next few days.

Tazawa has impressed since the moment he arrived in spring training. His four-pitch arsenal and deceptive, toppling-over delivery have made him difficult for hitters, especially those seeing him for the first time. He carved up opponents in spring training, and since then has been dominant in Double-A and strong in Triple-A. Tazawa is still young (23 years old), and perhaps could have used a few more weeks of seasoning in Triple-A, but general manager Theo Epstein said Tazawa’s time has come.

“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,” Epstein said.

Jason Bay remembers facing Tazawa in live batting practice in Pawtucket, and being caught off-guard by the way the ball came out of his hand.

“He’s a guy who has a little deception, a little funk to his delivery. I don’t know what his numbers were like in the minor leagues, but especially with guys having not seen him, I think he’s going to do alright,” Bay said.

The Red Sox scouted Tazawa heavily and signed him to a $3.3-million, three-year deal this December. Tazawa had a 13-1 record and an 0.80 ERA in 21 games for Nippon Oil ENEOS of the Japanese Industrial league. Some wondered about the competition he faced in Japan’s equivalent of the minor leagues, and whether his talent would transition to the United States.

Tazawa’s talent has exceeded expectations so far, but it’s his maturity that has truly impressed the Boston brass, particularly Francona.

“He’s a little bit of a unique guy. I mean, again, he came to camp this spring –– I had never seen him pitch in person. He handled everything. The game didn’t look like it was going too fast. If you have the stuff, sometimes when you don’t have experience, the game speeds up. That’s natural. But it never has, at least to this point it hasn’t done that yet. ... What it looks like is he’s an extraordinary young man,” Francona said.

Tazawa has spent his time in the minor leagues fine-tuning his approach to pitching, focusing on learning to trust his fastball more. Tazawa’s off-speed stuff is so good that in the past, when he hasn’t gotten strike one, he’s moved away from his fastball and leaned on his other pitches to get inferior hitters out. That won’t always work at the major-league level.

So Tazawa has worked hard to lean more on his fastball, which itself is an excellent pitch.

The right-hander was named to the Eastern League All-Star Team after going 9-5 with a 2.57 ERA in 18 starts at Portland. He made the leap to Pawtucket only a few weeks ago, posting a 2.38 ERA and six strikeouts in two losing starts.

It’s too early to know whether Tazawa is with Boston to stay, but if he pitches well enough, he certainly could force the Sox into keeping him up here. Epstein had always hoped to see Tazawa debut as a 40-man roster addition in September, so if he proves himself now, it wouldn’t be far off the original timetable.

“We’ll see. 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," Epstein said.

******

Paul Byrd, the catastrophic option backing up the Sox’ regular insurance policies, reported to Fort Myers on Friday and could be helping out Boston, if needed, in roughly three weeks.

Byrd, 38, agreed to a minor-league contract with the Sox on Tuesday night. The longtime starter spent time with Boston last season, but decided he didn’t want to pitch for the first half of 2009. He said he would return in the second half if the right opportunity presented itself, but then no one called.

“He was throwing and working out consistently, expecting a call in June or July from a club and then stopped throwing about two weeks ago,” general manager Theo Epstein said.

The Red Sox have seen their vaunted starting pitching depth crumble in recent days, and they phoned Byrd to inquire about his status. He immediately got up and went back to work.

“When we first called him a few days ago, he started again and was able to throw two innings against a college team,” Epstein said.

Byrd will need to do conditioning and throwing work to prepare for game action, and it’s not clear if the Red Sox’ rotation will work itself into shape without him. But if he’s needed he could be ready by the end of the month.

He’s got some work to do to get in game condition and to get his arm into shape. He’s probably about three weeks away from being able to help.”

Byrd has 108 victories and a 4.38 ERA in 13 seasons.

******

With his return to the rotation more important than ever, Tim Wakefield threw Friday, and strength is returning in his weakened left calf muscle.

Wakefield went to the disabled list July 21 after hurting his lower back, at the same time that his torn-up shoulder was beginning to show signs of wear and tear.

But while the back has healed and the shoulder feels strong, Wakefield has experienced weakness in his left calf that is hindering him from moving around well and fielding his position. The calf injury is nerve-based, related to the lower back injury. It is believed that the back strain put pressure on the sciatic nerve running down the back and leg, and sapped his power.

Now Wakefield is starting to show signs of regaining strength in the area, Francona said.

“The good news is that his arm feels great and all that. But we don’t want to send him out there and jeopardize having him pick up a bunt and hurt something. And if it hurts there’s a reason, but it is getting a lot stronger," Francona said.

If Wakefield continues to show improvement, he should face hitters Monday in a simulated game at Fenway Park.

“The deficit from one leg to the other is certainly a lot improved the last couple days, and I think we’re hoping it will continue that way,” Francona said.

dbarbari@projo.com