Formula One heads to Canada for the seventh round of the season this weekend, with Sebastian Vettel leading the drivers' standings by 25 points from Lewis Hamilton.

While the competition is heating up at the front end of the grid, there has been plenty going on elsewhere in the world of F1 since the last race in Monaco.

With that in mind, we take a look at some of the storylines to have emerged over the past fortnight.

KUBICA BACK IN AN F1 CAR

It has been six years since Robert Kubica last drove a Formula One car but the Pole is due to get behind the wheel of a 2012 Lotus for a test on Tuesday.

Former BMW Sauber and Renault driver Kubica suffered hand and arm injuries in a rallying accident in 2011, bringing a halt to an F1 career that had seen him achieve 12 podium finishes, including victory at the 2008 Canadian Grand Prix.

The 32-year-old has largely focused on the World Rally Championship since 2013 but has made a return to single-seater driving by testing GP3 and Formula E cars in recent months.

And Kubica will climb back into an F1 car in Valencia on Tuesday, at the same circuit where he last drove one of the machines, just days before his serious accident.

GIOVINAZZI SET FOR HAAS PRACTICE

Ferrari third driver Antonio Giovinazzi was given the opportunity to prove his talents earlier this season when he stood in for injured Sauber man Pascal Wehrlein for the first two rounds.

A creditable 12th-place finish in Australia was followed by a considerably less impressive spin into the wall in the wet in China.

But the Italian is now set for more track time after it was revealed he would take part in seven FP1 sessions for Haas, replacing Kevin Magnussen in six of them.

The announcement follows news that Sauber would switch from Ferrari to Honda power from 2018.

F1 CALENDAR EARMARKED FOR SHAKE UP

F1 bosses are to take a more proactive approach to growing the calendar as they push to expand a schedule that will feature 21 races in 2018.

Speaking to Autosport, marketing chief Sean Bratches also explained that he would like to see a reduction in back-to-back race weekends.

"Our view is that we'd like to go above 21 and we want to be a little bit more proactive and go on the offensive in terms of the markets where we go," he said.

"As we start identifying an optimal calendar in optimal regions, we can go down and sit with cities and make our case as opposed to what has been a little bit more reactive to bids coming in."

TORO ROSSO WANT MORE OF THE SAME IN 2018

We may only be six races into the season, but that doesn't mean teams aren't already looking ahead to 2018 and what their driver line-ups might look like.

And Toro Rosso boss Franz Tost said this week that he would be delighted to keep Carlos Sainz and Daniil Kvyat as his pairing.

"This is a decision for Red Bull. We have to wait. But if they continue with us it would be fantastic," Tost told Autosport.

Toro Rosso sit fifth in the constructors standings, ahead of Williams, Renault, Haas, Sauber and McLaren.