Fernando Alonso sent the racing world into a semi-expected meltdown with his retirement announcement on Tuesday, and his absence leaves a blaring gap on one of the most successful teams in F1 history, but who is going to fill it? Here are a number of possible options
#5 Carlos Sainz
Even before Alonso made his announcement, there had been speculation that his fellow Spaniard would be lining up alongside him in 2019. It is no secret that Mclaren admire Sainz, with chief executive Zak Brown saying that he would be high on the list for consideration.
With Daniel Ricciardo taking his seat at Renault for the new season, he is currently without a team. Of course, there is the possibility that he could make a return to Red Bull, given that he is a product of their young driver program and made his F1 debut with their junior outfit Toro Rosso. However, that seat is being fiercely contested by the likes of Pierre Gasly and Brendon Hartley, and he may prefer the option of going to Mclaren where he would be given priority, rather than Red Bull, where he would likely have to play second fiddle to their golden boy Max Verstappen.
#4 Lando Norris
Like Red Bull, Mclaren have their own young driver program. But unlike the drinks manufacturer, they don't have a sister F1 team with which to blood their new drivers. 18 year old Brit Lando Norris is one driver on their program and looks fairly ready for an F1 drive following his victory in the 2017 F3 Championship (he currently sits 2nd in the 2018 edition). With Max Verstappen demonstrating that youth isn't necessarily a barrier to success he could prove a good option for the 2008 world drivers champions.
Additionally, there have been murmurings that Mclaren are in a 'use him or lose him' situation with the young star, and if they don't put him in the car then another team (Red Bull also have an open seat) may have the right to swoop in and give him a drive. So there are a number of things to consider.
#3 Esteban Ocon
With Lance Stroll's billionaire father involved in a consortium takeover of Force India, all signs point towards the Canadian driver leaving Williams for the Britain-based team. That would mean that one of the two drivers currently racing for them would have to be given the boot. Ocon has impressed in his two seasons so far, but Perez is the more experienced of the two, and with the team needing to raise significant finances he could be the more attractive option given the brand appeal that he has in North America.
Ocon is a protege of Mercedes' Toto Wolff, but with Lewis Hamilton and Valtteri Bottas already signed up for 2019 there is no room for him on the 2017 world champions. The Red Bull seat is open, but they prefer to promote from within, and few other seats look available if he wants to race in F1 next year. A straight swap with Stroll would be another option but Williams is currently in a far worse place than Mclaren, for all the problems they've had.
#2 Robert Kubica
With the Pole making an unlikely comeback to F1 as Williams test driver in 2018 following 7 years away on the back of a career-threatening rally crash in 2011 he could probably view his chances of racing the Williams next year pretty high given the imminent exit of Lance Stroll and the poor performance of Sergey Sirotkin.
However, if the British team need to raise funds then they may be forced to go with a new set of pay-drivers in order to keep the company afloat. Mclaren, who paid Fernando Alonso a reported $25m last year, have no such trouble, and it could be attractive for him to race for one of F1s most glamorous teams on his return to the grid.
#1 Charles Leclerc
For a while, it looked certain that the Monegasque would replace Kimi Raikkonen for the 2019 season, but it now seems like the Finn will retain his seat for yet another year. Leclerc is part of Ferrari's own Driver Academy, but if he feels like they have overlooked him once again in favour of the 39 year old Raikkonen who is almost twice his age he may decide he's had enough of waiting.
If Mclaren can convince him they'll be competitive within a few years, like Renault appear to have done with Ricciardo, then maybe that will be enough to get the 20 year old to sign. Either way, the Mclaren seat would surely be better than another year in the improving, but not destined for great things, Sauber.