This is from a quick search on "Frans Nielsen leader". It was just after he signed in Detroit, and includes comments from Dan Saraceni, who is one of the two main writers for Lighthouse Hockey, the Islanders SB Nation blog:
Nielsen Ratings: Frans In-Depth
"It's easier to see what a player can do on the ice than off it, but we know how important the latter can be to a team. I asked Dan what intangibles Nielsen brings to the team, and his answer was very promising:
"He's worn an "A" for the Islanders for some time and
was a leader in the locker room. As far as I know, there's never been a cross word said about him, and his (now ex-)
teammates praised his unselfishness and reliability. Losing him is going to have a huge effect on the team's make up. To be honest, as a fan, I'm scared of just how much of an effect it will have."
So at a minimum, he had respect and was considered a leader with the Islanders.