With a host of top drivers locked in to contracts that take them up to 2021, F1 had initially look set for a more stable time.

But nothing stays still in F1 for long, and as the mid-season approaches, the paddock rumour mill has already got into gear as teams and drivers manoeuvre themselves for 2020.

One of the most fascinating aspects this year though is that the driver market does not just involve the current grid with a couple of rookie hopefuls looking to step up.

Instead there are two big names sitting on the sidelines who could play a pivotal role: Esteban Ocon and Fernando Alonso.

Mercedes junior Ocon was the unlucky victim of the Ricciardo move. The young Frenchman believed he had a deal in place with Renault for this year, with his 'manager' Toto Wolff having shaken hands with Renault's Cyril Abiteboul over the matter.

He lost out on that seat though and, with other opportunities having faded away, Ocon was left with little choice but to sit out this year and focus on his role as Mercedes reserve.

Efforts are now ramping up to get him back into F1, and insiders suggest there are a host of options for him.

Ocon's number one target is Mercedes, with Valtteri Bottas only on a one-year contract, which means the team needs to make a call soon on what it does for 2020.

Esteban Ocon, Mercedes AMG F1 Photo by: Mark Sutton / Sutton Images

Bottas' strong recovery after a difficult 2018 campaign appears to have killed off Ocon's chances of stepping in alongside Lewis Hamilton, but Wolff is clear that the incumbent still needs to keep up his game if he is to stay on board.

"Valtteri said to me last year that he has no problem with the one year extensions although he doesn't like them," Wolff told Motorsport.com.

"I think Valtteri merits a seat in F1 and he knows it is down to him and his performances, and we like him very much.

"The first quarter of the season was very strong. He just needs to just pick up the bag and continue to perform like he did, and this is what we both – him and us – agree on."

Should Bottas 'pick up the bag', then Mercedes-powered chances at Williams and Racing Point would be obvious for Ocon, but it is not definite that he needs to maintain affiliation to the German car manufacturer.

Wolff is clear that the time has come where, if Ocon's career rests on him cutting some ties to Mercedes, then it will need to be done.

"There is this perception that he is a Mercedes driver, so maybe we need to set the record straight and enable him to pursue his career in a way that respects the investment and the support that Mercedes has given him, and he respects that very much, but equally doesn't close doors for him," he explained.

Pushed on whether that meant being released from his Mercedes commitments, Wolff said: "I think if he drives for another team he is released anyway. He is not a Mercedes driver any more because if you drive for another team you are signing a contract that you will deliver to the best of your abilities for the other team."

Switching manufacturer camps could put Ocon in the frame at Renault once again, with the team pondering whether to commit to Nico Hulkenberg again.

Nico Hulkenberg, Renault F1 Team R.S. 19 Photo by: Zak Mauger / LAT Images

Having a Frenchman on board could be of particular attraction to the French car manufacturer, plus Ocon would likely agree to a cheaper deal than Hulkenberg.

But there could also be an opening for Ocon at Haas, with the future of Romain Grosjean again in doubt after a difficult start to the campaign.

Grosjean has scored just two points this year, compared to teammate Kevin Magnussen's 14, and the team may feel that the time has come for a change to move itself forward in the increasingly tight midfield battle.

Another option for Haas could be Sergio Perez, who was a contender for a seat with the team this year before he committed to staying at Racing Point again.

But with Racing Point having a more difficult campaign than anticipated, and Perez knowing that time is ticking on his career, he could face a tough choice this summer on what he does for 2020.

Should Perez up sticks, then Racing Point would be an obvious place for Ocon. But equally, some have suggested that team owner Lawrence Stroll could put together a Canadian super team and take on Nicolas Latifi – who has also been linked with Williams.

But it's not just the midfield that has potential for change, because the front of the grid may not be as settled as many think.

Pierre Gasly's struggles at Red Bull have already cast doubt over his future at the outfit if he cannot turn things around over the remainder of the campaign.

Should the Frenchman get dropped then Daniil Kvyat's return to Red Bull would seem the most obvious solution, especially with Red Bull's worries about losing Max Verstappen now easing after his win at the Red Bull Ring.

But wild rumours in Austria even suggested Sebastian Vettel was a contender there based on his more frequent visits to the Red Bull energy station.

#8 Toyota Gazoo Racing Toyota TS050: Fernando Alonso wins the Le Mans 24 Hours and the FIA World Endurance Championship Super Season 2018 / 2019 Photo by: JEP / LAT Images

Quietly sitting in the background of all this is Alonso who, with his McLaren Indy commitment and Toyota WEC duties now over, is pondering his next career step.

F1 is certainly not a closed door for the Spaniard, even though he would only return if he could guarantee himself a car capable of fighting at the front.

The message coming out of McLaren is that its future is now firmly with Carlos Sainz and Lando Norris, so there is no opening there now for Alonso. With that route shut off, the outfit would be unlikely to block him doing a deal elsewhere.

Paddock insiders suggest that Alonso has been sounding out Ferrari on where it goes from here, even though officially the team has both Vettel and Charles Leclerc under contract for 2020.

But is Vettel fully committed for next year, or is he having second thoughts about what to do after a difficult campaign? Only he will know the full truth of this.

Were he to go, then there are not many instant options that could be slotted in, with so many top-line drivers locked down until 2021. So, if you are after a quick driver who would take a one-year deal, Alonso would not be a silly choice.

An F1 comeback for Alonso at Ferrari would certainly be unlikely, but in F1, you can never say never.

And, as Ricciardo showed us last year, driver market bombshells can be dropped at any time. Don't rule out this silly season being as explosive as the last.