A spokesman for TSN would not discuss how the offensive tweet, which ran on a live crawl at the bottom of the screen, made it to air.
But Greg McIsaac did say "going forward TSN will not be airing public tweets during our live broadcasts."
The network read an apology on the air Tuesday night after a lawyer representing Phaneuf, his wife Elisha Cuthbert and Lupul threatened legal action.
TSN said the tweet was broadcast despite protocols to prevent unfounded and inappropriate social media posts from running on the air.
The lawyer representing Phaneuf, Cuthbert and Lupul said when offensive tweets are broadcast on reputable media outlets, they become much more harmful.
"I can tell you in the case of the three of them, Joffrey, Dion and his wife Elisha, they were humiliated, they were embarrassed, they were outraged that this could have happened," said Peter Gall. "That it had gone beyond somebody sitting in his basement... that it could go from that to being on your television screen for everybody to see. It was quite shocking and devastating."
The Twitter user who posted the tweet, Anthony Adragna, has since deleted the offending post and has tweeted that he had no control over it ending up on TSN.
Gall also sent a letter to Adragna demanding an apology and threatening legal action. He said Wednesday he hasn't received an apology.
Adragna hasn't responded to interview requests via Twitter.