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BOSTON - On the day before Class AAA Rochester started its season, manager Gene Glynn gathered his players in the clubhouse and asked everyone to introduce themselves.

One of the new pitchers in the Twins organization stood up and said, "Hello, I'm Sam Deduno, and I throw a crazy fastball."

Deduno explained that sometimes his fastball cuts toward the left-handed batter's box and sometimes it runs in on righthanders, adding that not even he really knows its direction when it leaves his hand.

Everyone had a good chuckle, but nobody was laughing Thursday night -- especially the Red Sox -- as Deduno tossed six strong innings, leading the Twins to a 5-0 victory at Fenway Park.

Red Sox starter Jon Lester (5-9) wasn't bad, allowing three runs over eight innings, but his offense gave him no help, getting just two hits for the whole game.

The Twins grabbed a 2-0 lead in the third inning on an RBI double from Denard Span and an RBI single from Ben Revere. Ryan Doumit added an RBI double in the sixth, and Brian Dozier added a two-run homer in the ninth.

Deduno (3-0) walked four hitters, had one strikeout and threw just 50 of his 101 pitches for strikes, but the 29-year-old rookie lowered his ERA to 2.48.

"If you start looking at the percentage of strikes and balls, you're going, 'Oof, how long's he going to be able to make it through this?'" manager Ron Gardenhire said. "But the one thing he has going for him is, he has some nasty stuff."

The Twins can't say they saw this coming. At least not with straight faces. They signed Deduno as a six-year, minor league free agent in November after the San Diego Padres let him go.

Deduno has a sharp curveball, but his walk rate -- 5.1 walks per nine innings through his eight-year minor league career -- always kept teams from getting too excited.

"I'm still working on control of my fastball, because I walked like four people today," Deduno said. "If I keep working, I feel I'm going to be better. My curveball and slider are pretty good; I'm still working on my fastball. The movement, it's crazy."

In 2009, he was named Texas League Pitcher of the Year, and Baseball America ranked him as the No. 11 prospect in Colorado's system. He reached the big leagues briefly in 2010, making four relief appearances, but the Rockies waived him that winter.

The Twins are his third organization. With Class AAA Rochester, Deduno went 1-2 with a 2.14 ERA in nine starts, but his walk rate was 4.7. So far with the Twins, it's 6.2, which is about twice the major league average.

"I'm not going to sit here and second-guess this kid tonight," Gardenhire said. "He just pitched six innings and gave up, what, two hits in this ballpark? He can do whatever he wants to do if he can continue stuff like that."

The Twins have instructed their catchers to sit behind the middle of the plate, instead of shifting their glove over the corners. Without knowing if the pitch will tail in or away from the hitter, it's better to play it safe.

"It's kind of like [catching for knuckleballer R.A.] Dickey," Twins catcher Joe Mauer said. "It's unpredictable a little bit."

But so far, hitters are having a hard time tracking it, too, and the Twins are going to ride this out as long as they can.