"I'm not proud of the game today, but I think there's a trade-off" for the spectators, Mr Calrsen said ahead of the final day of competition.
Mr Karjakin has described winning as "really important for me personally and for my country".
The intense match echoes a similar drama fought in 1972 between American Bobby Fischer and Russian Boris Spassky, who played in Iceland at the height of the Cold War in a televised game that dominated front pages for days.
This time, the game comes as tensions increase between Russia and North Atlantic Treaty Organisation (NATO) states, with Putin recently moving nuclear-capable missiles to its territory near the Baltic Sea. NATO secretary-general Jens Stoltenberg, who is Norwegian, has denounced the "military posturing" and responded by building up forces of its own.
The Norwegian player has also enlisted the help of Microsoft in his preparations, amid fears Russia's notorious hackers could interrupt his top secret preparations.
"The element of surprise is vitally important in chess," Microsoft Norway's Vibeke Hansen told The Telegraph. "Therefore, it is critical that all communication during preparation and the finals is completely secure. Preparing for a World Championship demands a lot of work, analysis and strategic sparring - and a lot of computing power."
On Wednesday, the men will play four rapid games, which the World Chess Federation says will be played "at the rate of 25 minutes per player per game, with 10 seconds added after each move".
It's much faster than previous games, which allowed for more than three hours of play. In the event of a draw at the end of those four games, the players will participate in two blitz games, a fast format played at the rate of five minutes per player at the start, with three seconds added after each move.
If it is still a draw, they will play another set of four blitz games.
"If there is still no winner, Carlsen and Karyakin will play an Armageddon game in which white has five minutes and black has four, but black only has to draw to win the match," the World Chess Federation said.
The faster games leave plenty of opportunity for harried mistakes. But in the meantime, Carlsen said "25 minutes and 10 seconds per move is a lot of time so we're still playing normal chess". "We're not at the penalty stage yet. We're at extra time," he said.
"I understand if sometimes both teams are not trying to score in the last minute of regulation that can be frustrating but also having extra time is exciting."
The winner will be declared world champion and will take home 600,000 euros (NZ$896,000). The loser will walk away with a consolation prize of 400,000 euros (NZ$597,500)
At the end of the eighth game, which ended in a victory for Karyakin, Carlsen left the premises in a state of fury before participating in a press conference, which earned him a penalty equal to 5 per cent of his earnings, whether he wins or loses.
