The Twins will also receive $500,000 cash as part of the deal.
"This makes us a better club," Twins general manager Bill Smith said. "Matt is a veteran closer, a veteran reliever and he's going to be a very good fit for this club. We've had an interest in Matt Capps for a long time, and this was a good opportunity for us to acquire him. It gives us a better chance to win the division and hopefully advance to the World Series."
Capps, 26, earned his first All-Star nod this season while pitching for the Nationals. He has recorded 26 saves in 30 opportunities and posted a 2.47 ERA in 47 games.
Capps will immediately take over as the Twins' closer and Jon Rauch will shift back into a setup role along with Matt Guerrier and Jesse Crain, Twins manager Ron Gardenhire confirmed on Thursday night after the deal was announced. Gardenhire said that he'd already spoken to Rauch about the switch.
"He was very professional about it," Gardenhire said. "He said, 'Whatever it takes to win.' It was the same thing he said to me when I told him he was the closer. He said, 'Whatever you need me to do, I'll do.' He said he just wants to win and be on a winner."
Rauch took over the closer role for the Twins when Joe Nathan underwent Tommy John surgery in Spring Training. Rauch has filled in admirably with 21 saves in 25 opportunities. But the righty was not considered to be a prototypical closer since he lacks overpowering stuff, and he posted a 5.40 ERA in nine appearances in July.
The acquisition of Capps will allow Rauch to slide back into the setup role that he filled successfully for the club last September, after the Twins acquired him in a waiver trade from the D-backs last August.
"This just makes our bullpen stronger," Gardenhire said. "You put Rauch in that setup mix and we've got this guy at the end, we can really shorten up a game if they're all throwing good. It could be a lot of fun."
The Twins currently trail the Chicago White Sox by 1 1/2 games in the AL Central, and they've spent the past month scouring the trade market for both starting pitching help and relief help in an effort to help them in the race.
The club was involved in talks for Cliff Lee, as well as other starters such as Roy Oswalt and Ted Lilly. But when those options looked like they wouldn't pan out, the club switched to a search for bullpen help.
Ramos -- who had been labeled as the Twins' No. 2 prospect -- was batting .241 with five home runs and 30 RBIs for Triple-A Rochester this season. He played seven games for the Twins this year when Joe Mauer was sidelined due to a bruised heel. During that stint, Ramos batted .296, which included going 7-for-9 in his first two games.
The Twins were not only impressed with Ramos' bat, but also his defensive prowess. The 22-year-old catcher had been considered to be the Twins' best trade chip, particularly after the club signed Mauer to an eight-year, $184 million extension in Spring Training.
And while Smith acknowledged that the team had to give up a very good prospect to get Capps, the club felt it was worth it to get an All-Star pitcher for not just this season, but 2011 as well. Capps signed a $3.5 million contract with the Nationals this winter, after the Pittsburgh Pirates did not tender him a contract. But he has one more year of arbitration eligibility left, meaning the Twins could have control of him through the 2011 season.
"Wilson Ramos is a very talented player, and he's got a bright future," Smith said. "To give him up, having that second year of control for Capps was a critical piece. We have an opportunity for a big year here, and adding Matt Capps to the bullpen only makes us a better team."
Testa, a reliever, was signed as a non-drafted free agent in 2008. He began this season at Double-A New Britain, where he was 1-4 with a 8.25 ERA in 21 games. He was moved to Class A Fort Myers, where he went 1-1 with a 3.30 ERA in 15 games.
While the Twins have strengthened their bullpen with this move, there is still time remaining before Saturday's 3 p.m. CT non-waiver Trade Deadline, and they could still explore other moves. Last year, the club made the majority of its moves in August, after the non-waiver Trade Deadline had passed.
"We've looked in both areas -- at starters and relievers -- and the thing is, you're just trying to strengthen your club, and this deal does that," Gardenhire said. "That doesn't mean that we're still not out there looking for other people. If there is something else, and a starter is available and he's better than what we have, that could happen, too. There are still plenty of options out there, and a lot more teams trying to make moves. But right now, this is a good move for us."