Pettersson, 19, was selected by the Flyers in the seventh round (No. 198) of the 2014 NHL Draft.
The 5-foot-9, 187-pound defenseman played the past two seasons in the Swedish Hockey League with Linkoping, where he played 62 games. Pettersson represented Sweden at the 2014 World Junior Championship, winning a silver medal.
For our team, as a group, we've never been this far before, and so it's just more lessons learned, and sometimes you have to go to the school of hard knocks to find out what works and what doesn't. We've got a young group. They've played some unreal hockey here to get us this far, and we showed if we're not going to play the proper way, a really, really good hockey team is going to beat you, and that's what they did. It's a lesson learned.
— Lightning coach Jon Cooper after Rangers win in Game 6 forced a Game 7 that will be played at Madison Square Garden on Friday