Frk gave the Red Wings a 1-0 lead with 2:34 left in the third period. Phaneuf tied it 1-1 43 seconds later.
In the Red Wings blew a lead for the second consecutive game but responded with a win. Detroit was up 2-0 in its opener against the Minnesota Wild on Thursday. The Wild tied it 2-2 before the Red Wings scored twice to make it 4-2.
"It was tough. A tough goal to give up," Nielsen said of Phaneuf's shot which appeared to deflect off Detroit defenseman Mike Green in the slot. "Just like Minnesota came back against us, we didn't go down at all. We just came out and kept playing. It's a good sign."
The Senators were 0-for-7 on the power play and are 0-for-12 in two games this season. The Red Wings went 0-for-4 with the man-advantage.
"I don't think you get discouraged and get negative about it, because when you do that you grip it a little more tight, and nothing comes from that," Phaneuf said of the power play. "We'll stick to it, we'll work on it, and we expect to get better at it."