The duo registered three points apiece as Czechia opened round-robin play at the 2022 IIHF Ice Hockey U18 Women’s World Championship with a convincing 4-0 win over rival Slovakia.
Sapovalivova scored twice, including the eventual game-winner. Trnkova had a goal and set up two others.
"There's good chemistry between us," Sapovalivova said.
Forward Tereza Plosova recorded a pair of assists for the Czechs, while goalkeeper Michaela Hesova earned the shutout with a 16-save effort.
After a scoreless first period in which Czechia survived three penalties including a 5-on-3, Sapovalivova broke the deadlock 5:31 into the second. The 16-year-old drove to the right side of the net and lifted a backhand over the shoulder of Slovakian netminder Laura Medvidova.
"We played better than in the first period," Sapovalivova said. "I was very happy when the first shot went in. (To score) the first goal in the whole tournament is amazing."
"I tried to go as close as I could to the defender," said Trnkova, who was named Czechia's player of the game. "It was a little lucky. When I saw the net, I just tried to shoot and hoped the girls could get a rebound there. But it was a lucky shot, so I was really happy."
Czechia tacked on two more in the third period to put the contest out of reach. A little less than five minutes in, Sapovalivova gathered the puck in the right corner and skated untouched to the edge of the crease before flipping it into the net.
The Czechs scored on the power play with 11:20 left in the third to go up by four. Defender Eliska Hotova fired a shot from the high slot which hit the crossbar and went in.
Czechia finished 1-for-3 with the advantage. It was a relief for Coach Dusan Andraskovsky, who noted the Czechs struggled on the power play this year.
"We're always working on it," he said. "It's a good feeling to score on the power play."
Medvidova faced 41 shots — including a game-high 16 in the second period — and finished with 37 saves to earn player of the game honours for Slovakia.
"She kept us alive. She was really, really awesome," Slovakia coach Gabriela Sabolova said. "Until the start of the third period, we still could win. We had a chance on the first shift in the third period. If we had scored there, it might be a different game. But we didn't score."
While trailing, Slovakia had two chances to get on the board — one on a 2-on-1 late in the second period, and another with 1:22 left in the contest, but Tatiana Blichova's shot went over the net.
Perhaps the best chance, though, game 10 minutes into the opening period when Adriana Dubova and Karolina Veverkova went off for tripping and hooking, respectively. Slovakia only registered a couple shots on the 65-second 5-on-3.
"When you have a power play at the start of a game, you have to capitalize on it," Sabolova said. "I think they were nervous a bit and didn't score."
Next on the schedule for Czechia is Germany on Tuesday at 16:00.
"We know how they play," Andraskovsky said. "I think we've got to play our system, believe in it."
Slovakia will face Switzerland in the 20:00 contest. For Sabolova, the key to rebounding from Monday's loss is getting back to basics.
"We'll try to force the girls to keep it simple, she said. "Play the pass, don't hold the puck so long and shoot more than today."