Brendon Hartley 

Following a very successful period in the World Endurance Championship, Brendon Hartley's return to single-seater racing has proven to be very tough. He's been well and truly outperformed by Pierre Gasly when the car has been capable of scoring points.  

At Bahrain and Monaco, Gasly made Q3 – while Hartley got knocked out in Q2 at Bahrain and Q1 in Monaco. The Frenchman kicked on to score points at those two events (Bahrain P4, Monaco P7) but Hartley didn't register a single point in either of those races. He finished over a minute behind stablemate Gasly in Sakhir. A huge crash in FP3 at the Spanish GP certainly didn't help his cause either. 

The New Zealander did manage to score a single point in Baku – and showed a big improvement in form last weekend in Canada to surely retain his drive for the French GP. However, only last week, BBC reported Toro Rosso tried to sign Lando Norris  and this shows that the Kiwi is under huge pressure to keep his seat for the rest of the season. He'll need more strong weekends like Montreal to have any chance of keeping it for the whole of 2018.  

At the time of writing this, he trails Pierre Gasly 1-18 in the WDC standings.  

Kimi Raikkonen 

As has been the case since his return to Ferrari for the 2014 season, Finland's Kimi Raikkonen is a man in danger of losing his seat at the end of the year. Things seemed to be different at the start of the current season as the 2007 World Champion showed some fantastic speed in Australia and could have easily taken pole in China and Azerbaijan if he put his best sectors together.  

3 podiums from the first four races suggested he might give Vettel more of a run for his money in 2018. Yet, things have quickly gone downhill in the last three events and a return to the previous form of recent years leaves his hopes of staying in F1 for another year in the balance. 

He's failed to qualify within 0.2s of Vettel since the Chinese Grand Prix back in April. His race pace in Spain, Monaco and Canada was extremely disappointing compared to his German stablemate. Last weekend in Montreal, he crossed the line almost half a minute behind Vettel. The Finn is 53 points adrift of his stablemate in the standings and trails him 1-6 in qualifying. 

With young Charles Leclerc getting better and better all the time and Raikkonen starting to show signs of underperforming again, Ferrari could well decide to put the young man from Monaco in their car for 2019. A big decision is looming and Raikkonen's career may well come to an end at the end of this season. 

As Martin Brundle said in his post-race column, ''Ferrari have to be concerned about Kimi. l know he's one of the most popular drivers around, but after another mistake in qualifying, he finished nearly 30 seconds behind his team-mate on Sunday. What are they going to do? In my view, Kimi has reached the end of the road. He still shows a flash of real speed from time to time but he can't relentlessly deliver the required race pace any more. 

Charles Leclerc looks the real deal to me. He is out-performing his Sauber car just like Alonso and Webber did in a Minardi, like Senna did in a Toleman and Schumacher in a Jordan. He stands out a mile and really impressed me a month ago in Spain when he didn't wilt with Fernando Alonso on his tail.'' 

Carlos Sainz  

2018 was meant to be the year that Carlos Sainz would step up and show Red Bull that he could be a future driver for them. Unfortunately for the Spaniard, he hasn't got the advantage on Nico Hulkenberg and the German has been the star in the Renault team so far. 

After joining the French manufacturer for the final four rounds of the 2017 season, Sainz trails Hulkenberg 1-7 (not including Hulkenberg's car issues in Spain this year and the German not taking part in Q2 in the USA last year) in their qualifying head-to-head battle. Hulkenberg's superb consistency across qualifying is something Sainz hasn't been able to match so far.  

It's been a similar story for the most part on Sunday's too. The German is 5-2 up in races and outscored Carlos by 32 points to 24 at present. Sainz has also taken some heavy beatings in Bahrain and Monaco – he ended both races over 30 seconds behind Hulkenberg (including letting him through in Monaco). The positives from Canada is that he tracked his German stablemate throughout the race and finished less than 2 seconds behind. 

Nonetheless, he'll need to be beating Hulkenberg more often in the upcoming events in 2018 to have any chance of proving to Red Bull or other top teams that he's worthy of a drive in years to come. Renault will want to see it too. The pressure is very much on. 

Max Verstappen, Romain Grosjean and Stoffel Vandoorne  are three of the other drivers under pressure and you can click on the links to read in-depth pieces about them.