Hosts Canada enjoyed a perfect day one while defending champions Sweden suffered a shock defeat to Switzerland at the World Men's Curling Championship in Calgary.
After beating Scotland in the first session, Brendan Bottcher's rink saw off Japan in a hard-fought contest 8-5 to take them to the top of the standings after the opening day of competition.
"There's a lot of games. There's going to be some high moments. There's going to be some low moments," Bottcher said.
Mouat and Dodds claim World Curling Mixed Doubles gold in Aberdeen
"I think what separates the teams that are going to be around on the weekend is they find a way to win when they're not playing their best."
Scotland got back to winning ways in the final session, as they accelerated away with a fifth end score of four points to beat Denmark 7-2.
But the shock of the day came as 2019 champions Sweden were beaten in a thrilling contest by Peter de Cruz's Switzerland.
A back-and-forth match saw the Swiss rink take a 7-5 lead in the ninth end, before Swedish skip Niklas Edin scored two in the tenth to take the game to an extra end.
During which though, Swiss fourth player Benoit Schwarz scored one point to take a brilliant 8-7 win.
"It's a big, big confidence booster. World champions, multiple world champions, probably the best team in the world. You don't beat them every day in the big championships," said Swiss skip De Cruz.
"It's been a long time since we beat them in a major tournament and hopefully we can keep it going."
Italy, Norway and Russia are the other teams to have won both of their games so far, with Italy seeing off China 7-4 in the final session, Norway beating the Netherlands by the same margin and Russia easing past South Korea 9-3 in the second session.
USA began their competition with a 5-4 win over China in the second session as Japan beat Germany 8-5.
Scotland gear up for semi-finals in style
'Still work to do despite Olympic quota qualification,' says Mouat