The 29-year-old forward is entering the final season of a six-year, $23.82 million contract he signed Aug. 16, 2012. He can become an unrestricted free agent July 1, 2019.
Simmonds had 46 points (24 goals, 22 assists) in 75 games last season playing on a torn pelvis he had surgically repaired after the Flyers lost to the Pittsburgh Penguins in the Eastern Conference First Round. He also missed seven games after tearing a ligament in his thumb on Feb. 18.
Simmonds has scored at least 24 goals in each of the past five seasons, and his 86 power-play goals since 2011-12 are second in the NHL to Washington Capitals forward Alex Ovechkin (131).
Hextall said contract negotiations could extend into the season if nothing is agreed upon before then.
"[Simmonds'] got the character that something like that is not going to affect him, not going to affect the team," he said.
