Fisher scored two of Ottawa's three power-play goals in the Senators' 3-2 victory over the Bruins 3-2 on Saturday night.
Chuck Kobasew had two second-period goals for Boston, and Thomas kept it close while Ottawa outshot the Bruins 45-19.
"They were throwing everything at me," Thomas said. "They had shots on the rush, passes from behind the net, slot shots, point shots. They did a pretty good job of mixing it up and throwing a little bit of everything our way."
With Boston's Marc Savard serving a penalty for hooking, Fisher broke a 2-2 tie off a rebound with 6:11 left in the game.
"We've got smart players that can move the puck around and shoot, so it was just a matter of time, I guess," Fisher said.
"[Thomas] made some good saves. We wanted to make sure we were getting pucks to the net and using our speed. They've got some big D, but we feel we're a little bit quicker. So, if we could chip it in and get in behind them, we could do a pretty good job."
Fisher scored both of his goals off rebounds.
"We kept it pretty simple really," Senators defenseman Wade Redden said. "We got pucks to the net and told Fish just to plant himself there."
The Bruins pressed to tie it in the final minute with Thomas on the bench for an extra skater, but an icing call forced Thomas back into the goal with 10 seconds to play, icing the win for the Senators.
"Timmy is the reason we stayed in the game. There's no doubt about that," Bruins coach Claude Julien said. "He stood tall for us and gave us a chance to get at least a point. Unfortunately, penalties ended up costing us and that was disappointing."
It took the Bruins less than five minutes into the second period to score twice and take a 2-1 lead. Kobasew scored his fourth and fifth goals of the season, his first coming at 1:04 when he took a pass from Zdeno Chara behind the net and stuffed a wraparound between Gerber and the post.
A little less than four minutes later, Kobasew moved in from the point and found a rebound in the slot that he blasted past Gerber to give the Bruins a brief lead.
Heatley scored the Senators' second power-play goal of the night when he took a hard pass from Wade Redden and drilled a one-timer past Thomas.
"That was a great shot," Redden said. "The puck came around the wall and I had a little time. He had his stick up in the air ready so I just fired it to him and he made a great shot to beat [Thomas]."
Julien coached his 250th NHL game ... Fisher's first-period goal was the 200th point of his career. ... The Senators are a perfect 11-0-0-0 on the season when they score first, and 0-1-0-0 when they don't.