Wells missed 12 games because a right adductor strain. In four rehab appearances with Class A Potomac, Wells gave up one run in five innings. Before the injury, Wells was 0-2 with a 6.26 ERA for Washington.
Before he was sent down, Bergmann was 0-1 with a 6.91 ERA in 14 appearances with the Nationals.
Acting general manager Mike Rizzo said that Bergmann's performance against the Rays in Saturday's 8-3 loss played a role in his demotion. Bergmann's gave up a 2-1 lead and didn't record an out.
"Performance has a lot to do with it," Rizzo said. "The fact that he has an option obviously has something to do with it. We feel Jason is a big part of our future. We want him to go down there and work on executing his pitches.
"The Jason Bergmann that came up this time was much more focused and much better prepared. We are hoping the next time he comes back to the Major Leagues, he'll perform at a much higher level."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.