Kensing, 26, joined the Nationals on Wednesday afternoon and will be available to pitch in the middle innings, according to manager Manny Acta. This season, Kensing pitched in six games for Florida and gave up eight runs in 7 1/3 innings. His best season was in 2008, when he went 3-1 with a 4.23 ERA.
"We like him. He is a guy who has a pretty good arm. We have seen him for a couple of years in our division," Acta said. "We are trying to stack up some power arms and do whatever we can to get this bullpen going.
"There is no setup role for him right now. We are going to try to get a feel for him first in the middle of the games and see what he could do for us. He is not coming in here with any role."
Kensing found out about the trade Tuesday at 11 p.m. ET. He boarded a flight from Miami to Philadelphia on Wednesday.
"I'm excited. It's always good to have a job," Kensing said. "Things [on the field] didn't happen the way I wanted to early in Florida. But the team gave me another chance by sending me here. The Nationals have a real good lineup to pitch for."
To put Kensing on the roster, the Nationals optioned right-hander Jason Bergmann to Triple-A Syracuse and placed Roger Bernadina on the 60-day disabled list. Acta said Bergmann wasn't happy about hearing the news.
Bergmann, 27, had a 3.60 ERA in three relief appearances with the Nationals, after he was recalled from Syracuse on April 20. Although Bergmann had a better showing on the mound than reliever Saul Rivera, the team felt Rivera has a good enough track record to keep him around.
"We don't want anybody to be happy when they are sent down," Acta said. "The move wasn't about Bergmann. It was about making room for Logan over here. Bergmann has to continue to throw the ball over there like he has been throwing it. I'm sure we'll see him again.
"Saul was the best middle reliever on this team for the last three years. Compiling over 70 appearances during the last two years has to account for something. Saul [is] having a rough time. We feel we can get him back on track and be valuable again."
As for Gunderson, the Nationals selected him in the 48th round of the 2007 First-Year Player Draft. At the time of the trade, he was pitching for Class A Potomac and was 2-0 with a 2.84 ERA in five relief appearances.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.