Biron, 23, is required to be sidelined for a minimum of seven days.
The 6-foot-6 Biron had a goal and eight assists in 34 games last season for Florida.
The Panthers recalled right wing Jaroslav Bednar from the American Hockey League to replace Biron.
Bednar, 26, was assigned to San Antonio last Tuesday and had two goals and one assist in two games.
After months of strained negotiations, Havlat and the Senators agreed on a one-year, $1.6 million deal Saturday. Earlier this week, Havlat threatened to return to his native Czech Republic.
"It's great to be on the ice with the guys and play hockey again," Havlat said. "Every year, it's the same thing with a different player. It's over now, and I'm happy to be back in the dressing room."
Havlat had 24 goals and 59 points in 67 games last season. Assistant coach Perry Pearn said Havlat could play Wednesday night in Los Angeles.
"We're pretty excited to see him, and he's pretty excited to be back," center Mike Fisher said. "He just wants to play, and it's nice they got the deal done."
Information from The Associated Press was used in this report.