The person spoke on condition of anonymity Sunday night because the move hadn't been announced.
Dallas fired Nieuwendyk on Sunday after four seasons with two coaches and no playoff appearances. The Stars finished their season 22-22-4 Saturday without earning a spot in the playoffs for the fifth season in a row.
Nill has helped the Detroit Red Wings extend their postseason streak to 22 straight appearances. He was Detroit's assistant general manager for 15 seasons and has worked for the franchise's front office since 1994.
The Stars have scheduled a news conference for Monday to announce their new general manager. The team has refused to comment on reports that Nill would be Nieuwendyk's replacement.
"Joe Nieuwendyk has represented the Dallas Stars extremely well as the club's general manager and has helped put pieces in place that will once again turn this team into a contender," owner Tom Gaglardi said in a statement.
"However, I believe it is time to take this organization in a different direction with our intentions set on returning to the elite of the National Hockey League. ... I am confident we have found the right general manager to return us to the pathway of success."
Nill led the Red Wings' amateur scouting department and oversaw decisions made at the NHL draft. While working for the franchise, the Red Wings won four Stanley Cups between 1997 and 2008.
The native of Hanna, Alberta, played in 524 NHL games for St. Louis, Vancouver, Boston, Winnipeg and Detroit and had 58 goals and 87 assists in his career. He was an amateur and pro scout for the Ottawa Senators for three seasons before being hired by the Red Wings.
The future of coach Glen Gulutzan wasn't addressed by the team.
Dallas holds a contract option for a third season for Gulutzan, who is 64-57-9 in his two seasons after ending the lockout-shortened regular season with a 3-0 home loss to Detroit. The Stars dropped their last five games, and won only once in their last seven after a five-game winning streak.
When asked about his job security after Saturday night's game, Gulutzan said that wasn't under his control and that he'd continue to work for the Stars until told otherwise. He also praised Nieuwendyk.
"All I can say is that Joe's been tremendous for me. I think he's done a hell of a job," Gulutzan said. "You can see with our farm team and the young guys that we have here."
As a player in Dallas, Nieuwendyk won the Conn Smythe Award as playoff MVP in 1999 when the Stars won their only Stanley Cup.
When hired by Nieuwendyk two years ago to replace the fired Marc Crawford, the 41-year-old Gulutzan had never coached in the NHL. Gulutzan had been a successful minor league coach, including two seasons with the Texas Stars, the team's primary AHL affiliate.
The Stars weren't officially eliminated from the playoff chase until Thursday night, while playing their second-to-last game. They managed to stay in postseason contention even after longtime captain Brenden Morrow was traded, a week before 41-year-old points leader Jaromir Jagr and Derek Roy were dealt away at the trading deadline.
Dallas got several young players and extra draft picks in those deals.
Within days after Jagr and Roy were traded, the young Stars went on a season-best five-game winning streak.
Morrow waived his no-trade clause to go to Pittsburgh, which entered the playoffs as the No. 1 seed in the Eastern Conference. Morrow's rookie season in Dallas was 1999-2000, when the Stars were Stanley Cup runners-up a year after their title.
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