CINCINNATI - The Boston Red Sox acquired Cincinnati Reds closer Scott Williamson on Tuesday for a minor league pitcher, another player and cash.

The trade bolsters the Red Sox' bullpen as they try to overtake the New York Yankees in the AL East. Williamson, the NL Rookie of the Year in 1999, had converted 21 of 26 save opportunities.

Red Sox general manager Theo Epstein said Williamson has a fastball in the mid- to high-90s, along with a good slider and split-finger fastball.

''He's got three well-above-average pitches and it's really a potent combination coming out of the bullpen,'' Epstein said.

Williamson will be used as a setup man for closer Byung-Hyun Kim, acquired in a May 29 trade with Arizona. Williamson was a setup man for Reds closer Danny Graves until Graves was moved into the rotation this season.

''We're extraordinarily happy with the job that Byung-Hyun Kim has done as a closer,'' Epstein said.

Kim made five starts for the Red Sox before manager Grady Little shifted him the closer in late June, but Epstein said the possibility of Kim returning to the rotation and Williamson becoming the closer is ''remote.''

It was the Reds' first trade since they fired general manager Jim Bowden on Monday, leaving it to his aides to come up with deals.

''We've been talking to the Reds on and off for a week or two,'' Epstein said. ''Once they made their move in the front office, things really accelerated. … We got down to business very quickly.''

Williamson was the most attractive Reds player available in a trade. He avoided arbitration in the offseason by agreeing to a $1.6 million, one-year deal.

He had figured the club might deal another player who makes more money.

''I'm very surprised, to be honest with you,'' Williamson said. ''I'm just trying to figure out why they traded me. I'm not making as much compared to the other guys.''

The Reds got left-hander Phillip Dumatrait, a player to be named later and an undisclosed amount of cash. Dumatrait, 22, was 7-5 with a 3.02 ERA in 21 games at Class A Sarasota, but was not considered one of Boston's front-line prospects, Epstein said.

Boston is still looking to acquire another starter before Thursday's deadline for trades without waivers.

Reds players feared their front office wasn't done trading, either. They figured that once Bowden was fired, the franchise might move quickly to deal players before Thursday's deadline. Williamson learned of the trade in the bullpen during a 5-3 loss to Colorado.

''There's a lot of frustration going on in here right now, but hopefully we can right the ship,'' first baseman Sean Casey said. ''Until the trading deadline is over, I think everyone is kind of on edge.''