An Aircast was applied to Ekblad's left leg. Minutes earlier, Ekblad got caught up with Stars defenseman Esa Lindell in the corner following a hit from Lindell.
Panthers coach Joel Quenneville said after Florida's 4-1 win that Ekblad would undergo further evaluation on Monday, at which point the extent of his injuries should be known.
"We think he's going to be out for an extensive time," Quenneville said.
Panthers forward Jonathan Huberdeau said it was difficult to see a friend and teammate go down like that.
"He's hurt. He's probably going to be out for a while," Huberdeau said. "It's not cool. ... You hear him scream. It must have hurt so bad. I didn't really see it. I really didn't want to see it."
Huberdeau said teammates visited Ekblad briefly in a side room during the second intermission.
"Just went to give him a hug, tell him hang in there,'' Huberdeau said. "In the third period, we had to come out, play well and get the win for him.''
Panthers defenseman Keith Yandle said "it's never easy" to see a teammate get injured and helped off the ice but that it's on Florida's players to pick up where Ekblad left off.
"Anytime you miss a guy like that ... I don't know how long he's gonna be out, but it's one of those things where everyone has to step up and help fill those shoes," Yandle said.
Ekblad has 11 goals this season, tied for the most among NHL defensemen. He scored the winning goal in overtime Saturday night against the Stars.
"He's had so many games when he's dominant defensively, but it's his offensive contribution, joining the attack, added a different dimension to our power play,'' Quenneville said. "You couldn't ask for anything more.''
The Panthers were already playing their third straight game without captain Aleksander Barkov, who is sidelined with a lower body injury, and Patric Hornqvist, who is expected to miss a week with an undisclosed injury.
"I think there's a group here that has the ability to find ways to win hockey games, and we need to find out what it's like to win in the playoffs,'' Quenneville said.
ESPN's Greg Wyshynski and The Associated Press contributed to this report.