Iivo Niskanen put on new skis with 10 kilometers remaining in the 50-kilometer cross-country mass start race.
Russian rival Alexander Bolshunov did not.
The tactical decision proved to be the difference for Niskanen, who beat Bolshunov with a strong sprint to the finish and won Finland's first gold medal of the Pyeongchang Olympics on Saturday.
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Niskanen ended a long drought for his country in cross-country, becoming the first skier to win a gold medal in an individual event at the Winter Games since Mika Myllyla accomplished the feat in the 30-kilometer race two decades ago at the 1998 Nagano Games.
"It's a big deal for us," Niskanen said.
Bolshunov took silver and Russian teammate Andrey Larkov won bronze, marking the first time in 11 cross-country races that Norway has failed to medal at the Pyeongchang Games.
It turned into a two-man race with about 11 kilometers remaining as Bolshunov and Niskanen opened more than a 90-second lead over the rest of the pack. But while racing neck-and-neck, Niskanen changed skis with 10 kilometers left, while the Russian went ahead without him.
Niskanen sacrificed short-term loss for long-term gain — dropping about eight seconds in changing skis — but the moved proved to be a pivotal one.
With better wax on his skis, he caught up to Bolshunov and then blew by him with about 1 kilometer left. The Russian had nothing left to catch him and Niskanen won the marathon event in 2 hours, 8 minutes, 22.1 seconds — more than 18 seconds ahead of Bolshunov.
"I did not know (for) how many kilometers Bolshunov had used his pair of skis," Niskanen said. "Then I tried to catch him as soon as possible, and in the long downhill the fresh skis are much faster. Then I only needed to save energy at the end."
Bolshunov was upset with himself after the race, saying he could have won the gold medal had he not made the tactical error.
"With those skis I could not fight for the gold medal at the finish line with him," Bolshunov said. "It is just my fault."
Niskanen's strategy was to set a fast pace and he said it "worked perfectly."
"Iivo's just such a super athlete at the moment and his only focus is to win the gold medal here from this race," Finland teammate Perttu Hyvarinen said. "It's so nice to watch what he's doing and how he thinks about the goal. He's an amazing man and extremely strong."
It was another solid showing for the Russians, who swept all three medals in this event four years ago at the Sochi Games. However, none of those three medalists were invited to the Pyeongchang Games by the IOC.
Russian athletes are competing under the Olympic flag at the Pyeongchang Games rather than their own. They are also wearing neutral uniforms because the country's national federation was suspended for operating an elaborate doping scheme at the last Olympics.
Larkov was more than 2½ minutes behind Niskanen in third place, but still managed to take bronze by beating Alex Harvey of Canada and Martin Johnsrud Sundby of Norway.
Sundby said he was stunned by how far Niskanen and Bolshunov were ahead of the rest of the pack.
"What can you say, our group was almost three minutes behind — that is extraordinary," said Sundby, who will still leave the Pyeongchang Games with three medals.
The Norwegians raced without Johannes Hoesflot Klaebo, who decided to skip the final men's race of the Olympics and return home to Norway despite having a chance to become the only Olympian at the games to win four gold medals.
"After the team sprint I was not surprised, he looked tired," Sundby said. "I think he did the smart move. Now he's home celebrating his three gold medals."
Sundby said he will be rooting for Marit Bjoergen on Sunday to help Norway break the Olympic cross-country record for most medals in one Winter Games. Norway has won 13 medals so far, equaling the mark set by the Soviet Union in 1988.
"I think," Sundby said, "Marit will be hard to beat."