Richards managed 23 regular-season goals - eight fewer than the previous season - and just one tally in the postseason, when he played through pain.
Holmgren also revealed that winger Andreas Nodl missed the last nine playoff games because of a concussion. The Flyers had called it an "upper-body injury" during the playoffs.
Asked about a Twitter report that Pronger had a herniated disc in his back, Holmgren said, "We won't know his condition until we talk to the doctor on Monday."
Holmgren met with coach Peter Laviolette on Saturday to discuss the season and start planning for next season. He also plans to meet with the players individually and "come up with a game plan" for the offseason.
Despite winning just seven of their last 21 (7-8-6) regular-season games, the Flyers won the Atlantic Division and finished with the Eastern Conference's second-best record (47-23-12).
Does Holmgren foresee major offseason moves or just some fine-tuning?
"I think it's important to sit back and look at things" before making any rash decisions, he said.
Holmgren praised rookie goalie Sergei Bobrovsky, saying he was "really happy with the way his season came along."
The Flyers season may have ended, but winger James van Riemsdyk is still playing.
The second-year winger was added to the U.S. national team that is competing in the IIHF's World Championships in Slovakia.
In the Flyers' 11 playoff games, van Riemsdyk scored seven goals, which is tied for first among NHL players in the playoffs. He also leads the NHL with 70 playoff shots.
Boston forward Patrice Bergeron suffered a mild concussion in Friday's series-clinching win when he was hit in the third period by the Flyers' Claude Giroux, the Bruins announced.
Bergeron, who has a history of being concussed, has 12 points in the postseason, and he may not be available for the start of the conference finals against Tampa Bay.
Contact staff writer Sam Carchidi at firstname.lastname@example.org. Follow on Twitter at twitter.com/BroadStBull