sport news Formula One 2019 season preview - is this Lewis Hamilton's toughest Mercedes ...

Lewis Hamilton will be looking to make it six of the best as he prepares to defend his drivers' championship ahead of the new Formula One season.

The five-time world champion is again favourite to leave his rivals for dust over the 21-race campaign that starts at this weekend's Australian Grand Prix and ends in the Abu Dhabi desert in December.

But there are stories all over the 10-team, 20-driver grid and ahead of another season Sportsmail's reporters look at the key questions. 

Will Hamilton be facing his toughest fight yet at Mercedes to defend his title?

JONATHAN McEVOY: From outside the team, yes, but there will be no repeat of the internal battle with Nico Rosberg that needled him so much. Ferrari seem strong and Red Bull will develop well under design guru Adrian Newey’s hand. It should be a good fight. 

JOE DOWNES: Yes, because for the first time his best may not be good enough. Ferrari have the quicker car again, but will have learned from last year's strategy and development blunders and appear more united under Mattia Binotto.

DAN RIPLEY: The last couple of seasons have seen Ferrari end the Mercedes front row monopoly, and now they may now even have the edge. Hamilton is in for his toughest campaign since his first season at Mercedes but he will still be at the front.

MATTHEW SMITH: Every winter we suggest the rest of the field are catching up with Mercedes, and every season the German steamroller carries on regardless. Hamilton has his ruthless eye on history and, as much as the fan in me wants to see a tight title battle, championship No 6 looks to be on the cards. 

NATHAN SALT: I don’t think so. While Ferrari have been smart in recruiting Charles Leclerc, he lacks experience competing at the front of the grid. Sebastian Vettel remains his biggest threat but errors appear to be creeping into the German’s drives if last season is anything to go by. 

How under threat is Bottas at Mercedes given how much of a team player he is?

JM: Bottas should not be there now. He clearly failed last year. But he suits Lewis and makes for an easy life. Even allowing for that I think he needs to buck up if he is to survive the cut again. 

JD: He insists he can beat Lewis. He can't. One-year rolling deal proves he's simply keeping the second seat warm and they're queuing up to take it. Esteban Ocon is first in line.

DR: Strangely I consider his role close to perfect. Quick enough to bag points but passive enough to never rock the boat and hurt Hamilton's season the way Nico Rosberg used to. Why would Mercedes risk losing that dynamic by drafting in Ocon for instance, who loves a squabble with a fellow driver (ask Perez or Verstappen)?

MS: Bottas is in an odd situation – he’s in this race seat for what he brings to his team-mate, rather than what he can provide as a driver in his own right. I feel Mercedes will want to bring Esteban Ocon into the No 2 seat next season, unless the Finn produces a marked improvement on last season. 

NS: In short: not much. Hamilton must love having a ‘wingman’ like Bottas with him at Mercedes. The Finn took issue with Toto Wolff’s use of that word in Hungary last season but it is true. Unlike predecessor Nico Rosberg, Hamilton can rest easy knowing Bottas will never put himself above the team. Bring back Nico.

How much of a 'pest' could Charles Leclerc be to Sebastian Vettel's title challenge?

JM: Vettel has been given a public indication he is No 1. It remains to be seen how Leclerc operates in the more rarefied air of Ferrari - a different proposition from Sauber. I think Vettel, refreshed, will win the internal battle.

JD: This will determine the championship. Ferrari have set their stall out early, insisting they will favour Vettel. The early races suit Ferrari and so, if Leclerc makes the better start, Binotto will have an almighty headache. The 21-year-old is a future world champion and subservience does not a champion make. Just ask Seb.

DR: I'm convinced he has been brought in to replace Vettel and not Raikkonen, with the German instead taking Kimi's No 2 spot in the long run. Not that Ferrari will admit that. To me,  Ferrari lost faith with Vettel and his endless mistakes last term and have already made their move to start building the team around the Monegasque.

MS: I think this could be the story of the season. Leclerc was electrifying at times in a poor Sauber car last season. If he hits the ground running, I can’t see how Ferrari can force him to play second fiddle to Vettel, especially if the German does not pick up from his 2018 slump. Don’t rule out a Leclerc title bid. 

NS: A real pest. You would be hard pressed to find an F1 fan who was not impressed why Leclerc’s rookie season with Sauber. He regularly exceeded expectations in qualifying and with a far more competitive car at his disposal this season.

Will Max Verstappen finally have the machinery to launch a bid for the title?

JM: We’ll soon find out. But from testing they look third-quickest. The Honda engine is three per cent down on the Mercedes. 

JD: No. He's better placed without Ricciardo and Renault but, while Honda power should see them close the gap, boss Christian Horner admits reliability is a big unknown in the first year of their partnership. Like last year, expect the odd win and the odd blow up (from car and driver).

DR: Status quo I'm afraid for Max. Another great Red Bull chassis which just lacks the power unit punch behind it to trouble Mercedes and Ferrari on a regular basis. Still, it's good to see Honda looking like they have caught up a bit. F1 needs them to succeed.

MS: If engine suppliers Honda go from their embarrassment with McLaren to title winners at Red Bull, that would be among the greatest turnarounds in F1 history. Verstappen seems to finally have his attitude in the right place (the Ocon

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