When the cross-country skiers' World Cup starts in Ruka this weekend is a lot about Frida Karlsson and Therese Johaug.

Karlsson got his big break as a 19-year-old in the World Cup last spring, with three medals, one of which is a relay gold, and impressed when last weekend she won two races in the Swedish premiere in Gällivare.

Johaug won and impressed - of course - even when the Norwegian premiere was simultaneously decided in Beitostølen. The question is whether Frida Karlsson is already the rider who can seriously challenge Therese Johaug, who was virtually impossible to defeat last season.

- Frida Karlsson can probably do some great races and even win. But she won't be as stable at the top as Therese. She's too young. There will be a big difference between Johaug and Karlsson over the season, says Camilla Vesteng, longtime ski reporter at Norwegian VG.

Lost a race

She recalls that Johaug took her first World Cup medal as an 18-year-old, but that it then took a while before she became a truly stable top rider in the absolute world elite.

- To compare Frida, 20, and Therese, 31, is not right. However, you can compare them well when they were the same age. Then they are a bit similar - with light hair and great energy - so they will surely continue to be compared anyway, says Vesteng.

Johaug returned from an 18-month doping suspension a year ago and it took until the last World Cup weekend before she was defeated in a distance race. Then it was Stina Nilsson who, in a mass start, asked the Norwegian.

In the distance race with individual start, you have to go back to March 2016 to find a race where Therese Johaug did not stand as the winner.

- If everything is normal - no cases, rod breaks or bad skiing - I think Therese will win almost everything with an individual start this year, says Petter Skarstad, skiing expert at Norwegian TV2.

- But then the season schedule is a little more friendly for riders like Frida Karlsson and Stina Nilsson. There are lots of mass starts, hunting starts and tours - which suits several Swedish women skiers better than it suits Therese.

Minitour starts the season

Therese Johaug's status is extremely high in Norway. But there are also hopeful hopes that more riders will be able to squeeze the superstar from Dalsbygda this winter.

- Even Ole Martin Iversen (formerly Sweden's and now Norway's national team coach) has told us at VG that he hopes Therese will lose some more. Partly because of the excitement, but also because it would trigger Therese a little, says Camilla Vesteng.

The World Cup begins with a mini-tour in Ruka, where Friday's sprint is followed by 10 km classically on Saturday and a final hunting start over 10 km freestyle on Sunday.