He allowed another before the opening period had even reached its midpoint, and the Bruins found themselves staring down a 2-0 deficit as the sold-out Wells Fargo Center roared.
That was just the beginning of a long night for the Boston netminder. But Thomas made sure it was an even longer night for the Flyers.
They threw 54 shots on Thomas, including 22 in the third period alone and another 10 in overtime. But Thomas didn't let any of those shots get by him. He shook off his shaky start and saved the last 46 shots he faced.
"As the game went on I was just trying to work hard to get myself into the game," Thomas said. "By the time the third period came around, I started to feel really good and fortunately I was doing good at the right time because they got some shots and some opportunities. They kept me busy for the third period."
Thomas' stellar play gave the Bruins the chance to stay in the game. Boston rallied for two goals late in the first to tie it, then David Krejci scored the winner at 14:01 of overtime for a 3-2 victory and a 2-0 series lead. But Krejci never would have had the chance to deliver that dramatic tally if not for the 46 straight saves Thomas made after that second goal.
"He was by far the star of the game tonight," Bruins coach Claude Julien said of Thomas. "He made some outstanding saves, especially when they started coming at us and had some unbelievable scoring chances. He stood tall and he made some great saves. There's no doubt if it's not for Timmy we might not be standing here tonight with a win.
"But that's what goaltenders do for you in playoffs and that's what you like to see in order to build some confidence in your team," Julie added. "When you know your goaltender's there to bail you out it certainly builds a lot of confidence, and Tim has given us that."
The Bruins have had plenty of confidence playing in front of Thomas all season as he made history with a league-best 2.00 GAA and an NHL-record .938 save percentage. But even by his lofty standards, this night was different.
"Timmy was pretty sick, not just on that kill, but that whole game," Bruins defenseman Andrew Ference said. "There is nobody better than him. He is unbelievable.
"He hasn't missed too many nights, [but] tonight was special," Ference added. "He was incredible. That third period on was a clinic. I don't even know what to say anymore, he is just unbelievable."
Thomas did have one moment of doubt, however. When Krejci scored, the puck ricocheted so fast out of the net that the referees initially didn't rule it a goal. Play went on for several seconds until the next whistle, when a video review confirmed the game-winner had been scored. That produced almost as much relief as excitement for Thomas.
"I saw I think it was [Milan] Lucic put his hands in the air, so I immediately went like this [putting his hands in the air," Thomas said. "And then I saw [Flyers goalie Brian] Boucher's shoulders slump as if it went in. But then play went on and I'm thinking, 'Oh, no.' I already started to get that overtime win rush and I was actually thinking to myself that I hope they don't get another shot right away. I had to settle back down."
Thomas didn't want to get ahead of himself in celebrating Krejci's goal. And now he and the Bruins want to make sure they don't get ahead of themselves in celebrating their 2-0 lead in the series. They remember all too well how Philadelphia overcame a 3-0 deficit last year, as well as how the Bruins themselves lost the first two games at home against Montreal and came back to win the opening series this spring.
"It's better to be on this side of that," Thomas said. "We do know from the way we were able to come back last series that a 2-0 lead in a series doesn't mean that series is over. We still have a lot of work in front of us. As long as we take the same approach, one game at a time, one period at a time, one shift at a time, I think that's the right approach. So that's the way we'll approach it going forward."
That and having Thomas between the pipes has proven a winning formula so far.