The Stars finished 34-37-11 for 79 points, their second-lowest point total in a non-lockout season since the franchise relocated from Minnesota to Dallas in 1993-94. In 2015-16, the Stars had the Western Conference's best record and reached the Western Conference Second Round of the Stanley Cup Playoffs, when they lost in seven games to the St. Louis Blues.
"I want to personally thank Lindy for his commitment and professionalism over the four years that he served as our head coach in Dallas," Nill said in a statement. "Lindy is not only a highly respected coach, he more importantly is a great person and an outstanding family man whom I have the utmost respect for on and off the ice."
The search for a new coach will begin immediately.
The Stars reached the playoffs twice in four seasons under Ruff but couldn't deliver on lofty expectations this season.
"We could never get on a good run where you go 6-1 or 7-1, or you win five in a row. We never got that good run going," Ruff said Saturday. "I said [Friday] that the probably the biggest disappointment was there were games we really deserved to win if we finished some of the plays, didn't hit posts and missed empty nets to stay on a run or keep something alive. We didn't quite have the finish we had in the previous year."
The Stars also had injuries throughout the season to key players including forwards Patrick Sharp, Jason Spezza, and Jamie Benn. Other important role players, including forwards Antoine Roussel, Ales Hemsky and Cody Eakin, also missed time with injuries, and forward Mattias Janmark missed the entire season with a genetic knee disorder.
"This has been one of the most frustrating seasons when it comes to injuries," Ruff said during the season. "It seems like each time one guy comes back another one or two go down. It really has been something that you could have never planned for."
Ruff is fifth in NHL history with 736 wins. He was 165-122-41 in four seasons with the Stars after spending 15 seasons as coach of the Buffalo Sabres.
The Stars' new coach will be the 23rd in franchise history, eighth since moving to Dallas. Ruff is fifth in Stars history in wins and had the third-highest points percentage (.593) behind Ken Hitchcock and Dave Tippett.