Werth wasn't specific about the changes. The Nationals are season-worst seven games under .500 and batting just .229.
On Friday afternoon before the Nationals began a series with San Diego, manager Jim Riggleman said he met with Werth, who last December signed a seven-year, $126 million contract with Washington.
Riggleman said it was a good meeting and he didn't feel Werth was calling him out.
"I guess the short answer is no," Riggleman said.
"We've got to start winning ballgames," Riggleman said. "The losing that's taken place here the (last) couple of years -- that's got to change. We've got to change some things -- what we do -- how we play."
Riggleman, who was named interim manager on July 14, 2009, and was given the job after the 2009 season, said he had a positive conversation with Werth, though he declined to go into specifics.
"He used the word 'frustrating.' He's been around a lot of winning -- and we're not winning right now," Riggleman said. "Other players are frustrated, and Jayson's becoming one of the voices of the ballclub."
Werth, who played in the postseason the last four seasons with Philadelphia, was not available for pregame comment, and through a club spokesman, said he'd meet with the press after the game.
The Nationals are missing two key hitters, third baseman Ryan Zimmerman, on the 15-day disabled list following surgery May 3 to repair a torn abdominal muscle, and Adam LaRoche, who was put on the DL this week with a torn labrum in his left shoulder.
LaRoche hopes to avoid shoulder surgery with a few weeks of rest and exercises.
"Whether that's wishful thinking or not -- time will tell," LaRoche said.