Kensing was given the news by interim manager Jim Riggleman, pitching coach Steve McCatty and acting general manager Mike Rizzo, when the team arrived at Nationals Park Sunday night.
Kensing was 0-2 with a 10.71 ERA in 17 games for Washington.
On Saturday, Riggleman acknowledged that he was baffled by Kensing's performance as of late. In his past six appearances, Kensing has given up 12 runs over 7 1/3 innings. Riggleman doesn't think there is something wrong with Kensing's arm. In Saturday's game against Cincinnati, in fact, Kensing's fastball was clocked at 96 mph.
"Steve McCatty and I talk about it a lot," Riggleman said. "Something is easy to see for the hitter or Kensing is tipping his pitches, because when you throw that good and [the hitters] square the ball up on him like they have the past couple of weeks, something is wrong there.
"He throws too good to get hit that hard. We hope he gets it straightened out. We wanted him to have a clean inning and build on it. It just didn't happened."
To replace Kensing on the roster, the Nationals have purchased the contract of infielder Mike Morse from Triple-A Syracuse. Morse, who came from the Mariners in the Ryan Langerhans trade last June, hit .327 with six home runs and 31 RBIs for Syracuse.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.