The Sabres dropped to 0-7-1 at home, their longest home winless skid to open a season. The eight-game home drought is also the team's second-longest single-season skid, and four short of the franchise-low set in 1990-91.
The all-too-familiar "Fire Darcy!" chants, directed toward general manager Darcy Regier, were briefly quieted by Ott's power-play goal in the second period.
Defensive breakdowns contributed to the Sabres digging themselves a first-period hole.
Sabres forward Drew Stafford allowed Fiddler to drive untouched to the front of the net and then convert his own rebound to open the scoring.
Cole checked defenseman Tyler Myers off the puck to set up Seguin's goal that put Dallas up 3-1 with 2:08 left in the first period.
Otherwise, the night belonged to Ruff, the Sabres winningest coach, who took over in Dallas in June to replace Glen Gulutzan.
A cheer went up when Ruff first stepped on the bench before the opening faceoff. Ruff then received a loud and lengthy standing ovation during the first break, when the Sabres showed highlights of Ruff as a player and coach.
Ruff couldn't resist in glancing up the board, at times smiling and at another point biting his lip. Players from both teams joined in banging their sticks on the boards. Several fans brought Ruff jerseys and hand-drawn signs, among which read, "We love you Lindy," and "Welcome home."
As the camera panned to Ruff behind the bench, the coach acknowledged the crowd with a quick wave.
That was a distinct change for Ruff from the last time he was behind a bench in Buffalo. Ruff and the Sabres were booed off the ice following a 2-1 loss to Winnipeg on Feb. 19. Ruff hadn't set foot into the arena since holding a farewell news conference three days later.