The moves came a day after the Flyers learned that forward Jeff Carter would miss six weeks with a broken left ankle.
Nedved, 34, started the season with the Flyers but was demoted after going scoreless in six games. He recorded four goals with four assists in seven games for the Phantoms.
In parts of two seasons with the Flyers, Nedved has five goals and nine assists in 34 games.
"I had some thoughts about going back to Europe and playing for the rest of the season," he said. "But the main goal was to come back and play for the Flyers. It's happened, I'm happy about that and I'll take it from there."
Ellison, 22, has a goal and an assist in one game for the Phantoms after missing 11 contests while recovering from abdominal surgery. Potulny, 22, has one goal and two assists in seven games for the Phantoms. Grenier, 26, is scoreless with 16 penalty minutes in nine games for the Phantoms.