They didn't expect it to happen so quickly.
It was Ennis' first game back after missing 30 games with a groin injury that required surgery.
''It's great to have Enzo back. He's such a skilled player and he makes everyone around him better,'' Eichel said. ''It's awesome to see him back healthy. He obviously adds a new dynamic to our team.''
The Sabres snapped a two-game losing streak and beat the Stars for the first time in four matchups.
''They jumped on us early,'' Stars coach Lindy Ruff said. ''Their energy was a lot better in the game than ours was. That was about as slow as I've seen our team.''
The Stars entered the game ranked 29th in the NHL in penalty killing, and fell behind Buffalo by allowing two power-play goals in two chances.
Dallas has killed 74.3 percent of its penalties this season. Buffalo is at 74.4 percent after the Stars didn't score on their only power play.
Stars captain Jamie Benn showed his frustration late in the second period when he snapped one stick over his knee and smashed another one on the bench. Benn had three of the Stars' 12 giveaways. He has one point and is a minus-3 in three games since returning from a lower-body injury.
''I think it's contagious and it runs through the team,'' Benn said. ''So I definitely need to do a better job with body language and definitely my play on the ice.''
Ruff noticed Benn was struggling and took him off the top line in the third period.
''It almost seemed every time he had the puck, something bad happened,'' said Ruff, the former Sabres coach.
Eichel gave the Sabres a 3-1 lead 7:07 into the second period when he scored from the left side of the net on a power play. It was Eichel's first goal in five games. He scored again into an empty net with 9.3 seconds left for his third two-goal game of the season.
Buffalo built a 2-0 lead in the first 13 minutes.
Ennis took the first shot of the game and beat Lehtonen with a wrist shot from the right circle.
''I got a goal early, but I was still pretty rusty,'' Ennis said. ''I can play a lot better. There's still an extra step, a little more pop in my skating.''
McCabe got his first goal of the season on a power play with 7:26 remaining in the first when he intercepted Benn's clearing pass and took a slap shot from the high slot.
Buffalo's Taylor Fedun had a goal disallowed prior to the power play when it was ruled that Lehtonen touched the puck after a delayed penalty on Faksa for hooking.
Faksa poked in the rebound off Jiri Hudler's slap shot that hit the post to make it 2-1 with 4:46 remaining in the first period.
NOTES: Eichel set career highs with 10 shots on goal and 13 faceoff wins. The Sabres are 6-0-1 this season when Eichel scores. ... Sam Reinhart assisted on Eichel's goal and has 13 points in his past 13 games. ... Stars D Jamie Oleksiak missed his third straight game with a hand injury. ... Buffalo recalled F Cal O'Reilly from the minors on Saturday. O'Reilly entered the lineup in place of Nicolas Deslauriers (healthy scratch). ... The Stars allowed a goal on each of the first three shots in Saturday's 5-4 loss to Minnesota. They are 3-13-5 when allowing the first goal this season. ... The Sabres have won their past five games against Western Conference teams. ... Both teams played the first game of a back-to-back.
Stars: At Rangers on Tuesday
Sabres: At Toronto on Tuesday
Copyright 2017 by STATS LLC. Any commercial use or distribution without the express written consent of STATS LLC is strictly prohibited.