"I haven't heard anything about that. I don't know where it would come from." Riggleman said.
Acting general manager Mike Rizzo was not available for comment. It has been widely speculated that Acta's job could be in near-term jeopardy, but nothing official had been indicated to that end as of Saturday afternoon.
Team president Stan Kasten briefed the media and would not confirm nor deny the FOXSports.com report.
"Do you have sources that say that? So you're asking me to respond to another media report? That's kind of a silly thing to ask," Kasten said. "I would never talk about personnel. ... I've been asked that question by some media outlet almost every day since the first week of the season -- radio, TV, print."
Entering Saturday's action, the Nationals are 16-43, with the worst record in baseball.
According to one of the team sources, the Nationals have contemplated letting Acta go since late May but decided, first, to relieve Randy St. Claire of his duties as pitching coach on June 2. Washington hired Steve McCatty to replace St. Claire.
At the time, Rizzo said the team needed more of an old-school pitching coach, and it is unclear whether that maneuver would be given more time to possibly stabilize Acta's standing.
Based on the FOX report, apparently not, but again, that news is unconfirmed.
"I can confess to you how perplexed I am about this season, this team and the things that are going on," Kasten said. "And our record is really troubling to me every single day. And we continue to search for solutions.
"We've made some moves since Opening Day. And it's been great to see some of these moves have been paying off. I continue to be so optimistic about future, because as I watch the growth of this young rotation as we had hoped for, to see all of these kids come together with the great demeanor and almost preternatural composure, makes that future so bright."
Bill Ladson is a reporter for MLB.com. Carter Gaddis is a contributor to MLB.com and contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.