FORT MYERS, Fla. (AP) – Wily Mo Pena hits the ball with amazing power, if he hits it. Bronson Arroyo has shown he can be a reliable starter, if given the chance.

Both of those ifs can turn to realities after the Boston Red Sox obtained the slugging outfielder from the Cincinnati Reds for the right-handed pitcher on Monday.

Arroyo had been headed for the bullpen because of Boston’s deep rotation but now figures to play a key role on Cincinnati’s mediocre starting staff. Pena struck out on 37 percent of his at-bats last season, but Boston general manager Theo Epstein thinks that can drop.

“Pena strikes out on a rate basis more than anyone else in the big leagues,” Epstein said. “There is precedent for those (type) players developing a little bit more discipline, increasing their walk rate and becoming better all-around hitters as they adjust to the big leagues.”

Pena, 24, struck out more times last season (116) than Arroyo struck out opposing batters (100). But Pena also hit 19 homers in 311 at-bats.

“This guy has some crazy power, man,” said Boston DH David Ortiz, who rated Pena’s strength above his own. “I just feel bad for my man Bronson.”

Arroyo brings the Reds an ability to pitch a lot of innings and a flexibility, if necessary, to move to the bullpen. Last year he was 14-10 with a 4.51 ERA in a career-high 205 1-3 innings.

Both players in the trade appeared to be happy where they were – Arroyo with a team he enjoyed and Pena finally getting a chance to play regularly as Cincinnati’s everyday left fielder after playing no more than 100 games in any of his previous three seasons.

The right-hitting Pena will be Boston’s fourth outfielder with most of his playing time likely coming as a fill-in for left-hitting right fielder Trot Nixon against left-handed pitchers.

The Reds had to keep Pena in the majors the past three seasons, or place him on waivers, after he ran out of options in 2002 at the age of 20. He was just 17 when he signed a five-year major-league contract with the New York Yankees in April 1999.

“He hasn’t had time to develop” in the minors, Epstein said. “He’s still a really dangerous threat against left-handed pitching and we think he’s got a chance to develop into more.”

Pena said he was surprised by the trade.

“I just want to be on a team and play every day,” he said.

He could get that chance in 2007 since Nixon will be a free agent after this season. And left fielder Manny Ramirez’s contract ends in 2008.

Pena, who signed a one-year, $1.25 million contract for 2006, can’t be a free agent until after the 2008 season. He batted .254 with 19 homers and 51 RBIs last season and struck out 116 times with 20 walks. He played for the Dominican Republic in the World Baseball Classic and had four singles and three strikeouts in 10 at-bats in three games.

The trade improves the Reds on defense, not one of Pena’s strengths. Adam Dunn, who moved to first base when Sean Casey was traded to Pittsburgh, can return to left field, the position that he’s played most in his career. Scott Hatteberg, a free agent who played with Oakland last year, will play first.

“Signing Hatteberg was the key” to the deal, Reds general manager Wayne Krivsky said.

Without Arroyo, Boston still has Curt Schilling, Tim Wakefield, Josh Beckett, Matt Clement, David Wells and Jon Papelbon as starters.

Cincinnati needs the 29-year-old Arroyo to start, and Krivsky was willing to give up a raw talent who could develop into an outstanding power hitter.

“I can’t worry about that,” Krivsky said. “This trade makes us a better team now.”

It didn’t cost the Reds as much as other deals might have because Arroyo, who loved playing in Boston where he developed a following as a rock guitarist and singer, took a hometown discount when he signed a three-year, $11.25 million contract on Jan. 19. Epstein said the team didn’t agree not to trade Arroyo but told him no trade talks involving him were in the works at the time.

“I don’t think it was a huge factor” in Cincinnati’s decision to make the trade, Epstein said.

Krivsky said he and Epstein had been discussing a deal for three or four days.

The trade was completed one day after Arroyo’s only good outing in four exhibition starts. On Sunday, he allowed four hits, no runs and no walks and struck out four in five innings of Boston’s 3-1 win over Baltimore.

“Because we have depth, we might not have been able to get enough out of him” this season, Red Sox manager Terry Francona said, “and that’s not a knock on him.”

Boston had claimed him off waivers from Pittsburgh before the 2003 season, which he spent almost entirely at Triple-A Pawtucket. In 126 major league games, he’s 33-33 with a 4.59 ERA.

The trade was difficult “from a personal standpoint,” Epstein said.

“I really admire Bronson and have gotten to know him really well,” he added, but “if I allowed my personal feelings about a player or recognition that this player would prefer to stay in Boston … affect our judgment in what we thought was best for the organization, then I wouldn’t be doing my job.”