Athanasiou cut it to 2-1 at 6:39, taking advantage of a Montreal turnover and scoring short side. He has six goals in his past seven games.
"I was trying to look to the side like I was going to pass, hoping Niemi would read it that way and give me a spot to shoot on the short side," Athanasiou said. "I don't know if it worked, but I was able to get it in there."
Petry scored 19 seconds into the third period to make it 3-1, taking a pass from Tatar and scoring from the high slot. It was his first NHL goal in his hometown (born in Ann Arbor, Michigan).
"It was exciting to get one here in front of my friends and family," Petry said. "I made a big mistake last night, but I had a quick turnaround where I could park that game and focus on this one."
Red Wings coach Jeff Blashill was frustrated by the lapses on defense that led to Montreal's goals early in the second and third period.
"We gave them three easy goals," Blashill said. "We have to work like dogs to score goals, and we gave three away. We can't win that way."