Carruthers improved to 5-0 with a commanding 9-2 win over previously unbeaten Brendan Bottcher of Edmonton in the next to last round-robin draw while Howard beat Calgary's Matthew Blandford 5-2 in the last draw.
Carruthers struggled a little, just claiming a single with the hammer in the first end. But he took a 4-0 lead when Bottcher missed a nose hit for two in the second end, removed his own counter and lost his shooter to give up a steal of three. Carruthers then stole another two in the third end to make it 6-0.
Bottcher finally put a deuce on the board in the fourth end.
Carruthers is a Brier winner and world champion as second with Manitoba's Jeff Stoughton, but hasn't skipped much since juniors. He struck out on his own when the Stoughton rink disbanded.
Bottcher (4-1) is the 2012 World Junior curling champ and has had limited success at World Curling Tour events since he started with a win at the 2012 Red Deer Curling Classic. In last season's National in March he finished 1-4.
Bottcher's lead is Karrick Martin, son of Alberta curling legend Kevin Martin, who has put down his broom and picked up a microphone as a curling broadcaster with Sportsnet — which gave him a front-row seat Friday to watch his son in action.
Howard (5-0), meanwhile, scored single points in the first, second, fourth, fifth and seventh ends en route to victory.
In other late games, John Morris (3-2) of Calgary scored five points in the fifth end to top Winnipeg's Jeff Stoughton (2-3), 7-4.
Brad Gushue (2-3) of St. John's N.L., had a single point in the ninth end to get past Calgary's Kevin Koe (2-3), 4-3.
Olympic champion and hometown favourite Brad Jacobs (3-2) of Sault Ste. Marie, Ont., scored two points in the first end and two more in the seventh in a 5-2 victory over Toronto's John Epping (3-2). And Switzerland's Peter de Cruz (2-3) downed Rob Rumfeldt (0-5) of Guelph, Ont., 7-2 in six ends.
In other afternoon games, Charlottetown's Adam Casey (2-3) beat Mark Kean (1-4) of Stoney Creek, Ont., 9-2 in six ends. Casey trailed 2-1 after three ends before responding with a pick up of three in the fourth and fifth ends and two more in the sixth to seal the win.
Heath McCormick (3-2), of Blaine, Minn., got past Stoughton in seven ends 7-4.
Saskatoon's Steve Laycock (3-2) picked up four in the seventh end for a 9-5 victory over Winnipeg's Mike McEwen (3-2). And Jacobs grabbed a single in the seventh end and one more in the eighth to slip past Blandford 4-3.