Fowler tied it 2-2 at 7:48 when his wrist shot glanced off the inside edge of the post with Derek Grant providing a screen and made it 3-2 at 13:08 when he scored on a rebound.
"We started moving our feet a little bit, playing on our toes," Fowler said of the second period. "We sat back quite a bit in the first period and let them dictate the pace of the game, and that's not the recipe for success."
The Sabres only trailed for 35 seconds before Krebs tied it 3-3 off a feed from Jack Quinn at 13:43.
Krebs was moved up to the third line with Mittelstadt and Quinn before the game.
"You know when you give them the puck, they're going to make some plays," Krebs said of Mittelstadt and Quinn. "I just tried to make sure I was hard defensively so I could get them the puck, and they did their thing."
Mittelstadt scored short side on a wrist shot from the right face-off circle to move Buffalo back ahead 4-3 at 18:03.
"After we fall behind 3-2, our guys wanted to get back out there," Granato said. "That kind of exemplified how dialed in our guys were tonight and how determined they were."