Daniel Ricciardo's shock switch to Renault and Fernando Alonso's decision to quit Formula One at the end of 2018 blew the F1 driver market wide open over F1's summer break. ESPN looks at the remaining seats needing to be filled and who the candidates are.

Mercedes

Dan Istitene/Getty Images

Lewis Hamilton, Valtteri Bottas

Mercedes locked down its current driver line-up during its home race in Germany. Valtteri Bottas has been retained on another single year deal, while Lewis Hamilton will remain with the team until the end of 2020.

Ferrari

Charles Leclerc has been tipped as Kimi Raikkonen's replacement for 2019. GERARD JULIEN/AFP/Getty Images

Sebastian Vettel, TBC

As with the past few seasons, Kimi Raikkonen's future has been uncertain since the first race -- his contract expires at the end of 2018. The emergence of Ferrari junior Charles Leclerc at Sauber has fuelled speculation the Monaco native could be promoted to the senior team, but promoting a young driver is a risky move for a team which has been as pragmatic as can be when making driver decisions in recent seasons.

In June the BBC reported Leclerc had agreed to a two-year deal, although Ferrari has refused to comment on what it called "media speculation". It is worth noting that Raikkonen followed up that news with a string of five successive podiums and he happily played the team orders game -- after some initial confusion -- in Germany.

Recent changes to the Ferrari's hierarchy may prove decisive, with the late Sergio Marchionne's role filled by John Elkann and Louis Camilleri, a good friend of Raikkonen.

Red Bull

Pierre Gasly will be driving for Red Bull in 2019. Clive Mason/Getty Images

Max Verstappen, Pierre Gasly

Red Bull did not wait long to confirm its plans for 2019 after the Ricciardo news. The confirmation of Carlos Sainz to McLaren opened the door for the elevation of fellow junior driver Pierre Gasly from Toro Rosso. On the Monday ahead of the Belgian Grand Prix, the team made the announcement, meaning the French driver will partner Max Verstappen in 2019.

Force India

Lance Stroll looks likely to be driving for Force India in 2019. JUSTIN TALLIS/AFP/Getty Images

TBC, TBC

This has become a very interesting gap in the driver market. Lawrence Stroll's recent acquisition of the team means it is likely his son Lance will make the switch from Williams next season, meaning either Esteban Ocon or Sergio Perez will be driving elsewhere in 2019. There are even suggestions Stroll could be in line to move teams before the end of the current season.

The legal action taken by Sergio Perez at the start of July triggered the chain of events which eventually saved the team and allowed it to be sold to the consortium, but the influence of engine supplier Mercedes might work against the Mexican driver. As reported by Motorsport Magazine this week, Toto Wolff spent much of the final weeks of the season looking to move junior driver Esteban Ocon to Renault or McLaren as early as the next race in, but the Ricciardo move means the Frenchman's most coveted 2019 landing spot has gone. Ocon's best option for next year now appears to be staying put -- unless a deal with McLaren is still on the table. Perez will want to stay but it is unlikely Force India will push back against the wishes of Wolff given their close partnership with the current world champions. Watch this space.

Williams

Recent events have increased Robert Kubica's chances of completing his comeback to Formula One. Mark Thompson/Getty Images

TBC, TBC

With Stroll almost certain to be driving elsewhere next year, there's at least one seat up for grabs. Mercedes is keen to place its other junior driver, George Russell, the current Formula 2 championship leader, in one of these seats next season and it seems likely he will be at the team -- especially if he wins the F2 title. Mercedes could also place Ocon at the team if he is unable to remain at Force India.

Sergey Sirotkin has been hampered with the worst car on the grid for his rookie season but brings significant financial backing to the team, which may well be enough to give him another year. It is worth noting Williams will be losing both its Martini title sponsorship and the backing of Lawrence Stroll next season, meaning financial considerations will be high on the list of priorities when deciding the 2019 line-up.

Robert Kubica has also been waiting in the wings as reserve driver this season, gaining several on-track appearances in the process, and his chances of stepping up full-time have increased in recent weeks, although he still remains an outside bet for a 2019 drive.

Renault

Daniel Ricciardo's decision to leave Red Bull has triggered huge movement in the driver market and is likely to elevate Pierre Gasly to his current seat. Dan Istitene/Getty Images

Daniel Ricciardo, Nico Hulkenberg

After months of courting Daniel Ricciardo, Renault finally got their man in August after the Australian made the shock decision to switch to the French manufacturer for next season. The team had also been in talks with Mercedes about a loan deal for Esteban Ocon. The Ricciardo acquisition puts the Australian alongside Nico Hulkenberg, who was signed to a multi-year deal in 2017. Renault is one of two teams (including Mercedes) to have confirmed its 2019 line-up at this stage of the season.

Toro Rosso

Could Stoffel Vandoorne's F1 career continue as part of the Red Bull programme? Charles Coates/Getty Images

TBC, TBC

Ricciardo's move from Red Bull and Gasly's elevation has left Toro Rosso in a bit of a bind when considering options for next year. After his remarkable comeback to F1, Brendon Hartley has been uninspiring so far, although reliability issues and bad luck should be factored in to his difficult season. Whether the notoriously hard-to-please Helmut Marko is convinced Hartley has a long-term future with the team remains to be seen.

Earlier this year, Toro Rosso approached McLaren about its junior driver Lando Norris, but refused to take the Englishman on loan. It is unlikely Red Bull will want any deal for Norris while he is still contracted to a rival team and it may well turn its attention to Stoffel Vandoorne, who seems likely to be dropped by McLaren at the end of the current campaign. Vergne could be an outside shot after his comments at the weekend, although he is unlikely to want to move back to his former team given his previous failure to make the step up from there to Red Bull. Although losing Gasly will be a blow, Toro Rosso is at least in the luxurious position of being able to watch how the driver market unfolds at this point.

Red Bull junior Dan Ticktum does not currently have enough superlicence points to make the step up to F1.

In recent weeks, the ousted Daniil Kvyat is a leading contender for the seat. The Russian was dropped by Toro Rosso at the end of 2017 and has spent 2018 as Ferrari's development driver.

Haas

Out-of-form Romain Grosjean could be replaced by Haas in 2019. Mark Thompson/Getty Images

TBC, TBC

Kevin Magnussen has been one of 2018's standout performers and the team holds an option on his services for next season. It would be a big surprise if he was not retained as there is a clear willingness on both sides for the relationship to continue.

The future of Romain Grosjean is far less certain. The Frenchman's struggles this season have tested the patience of his team, although his improvements in the last few races may have helped his cause as team boss Guenther Steiner did not commit to driver talks before the summer break. However, Grosjean has picked a bad season to struggle for form, with such an open driver market and with the likes of Sergio Perez looking for race seats next season. Perez would make sense for the American team given his marketability in Mexico and North America and the fact he remains one of the best drivers currently not at one of the 'big three'.

McLaren

Lando Norris is currently racing in F2 and contracted to McLaren as a reserve driver. Xavier Bonilla/NurPhoto via Getty Images

Carlos Sainz, Lando Norris

It is clear McLaren feared Fernando Alonso would walk away from F1, as it spent much of this year (unsuccessfully) courting Daniel Ricciardo. CEO Zak Brown says the team came close to snatching the Australian away from Red Bull and Renault. There were also reports of an approach made to Kimi Raikkonen. For now, the team has signed Carlos Sainz to replace his compatriot, but it still has a seat to fill.

McLaren has confirmed Vandoorne will no longer race for the team in 2019, meaning McLaren will have an all-new line-up in 2019. Shortly after the announcement of Vandoorne's departure, the team confirmed that junior driver Lando Norris will be given his F1 debut in 2019, having earned a promotion after impressing the team during various Friday practice outings, test sessions and his F2 campaign.

Sauber

Italian driver Antonio Giovinazzi is a candidate for Sauber. SAEED KHAN/AFP/Getty Images

TBC, TBC

Half of this obviously hinges around the decision Ferrari makes in terms of Raikkonen and Leclerc. If Raikkonen stays put, Leclerc is likely to do the same, spearheading the ever-improving Sauber outfit. Although it would disappoint many pundits and fans, there are clear benefits from Ferrari's point of view of having its hottest young commodity continuing to excel at a team carrying the iconic name and badge of Alfa Romeo. There were suggestions Leclerc and Raikkonen could switch seats -- the former world champion has a soft spot for the team which gave him his break in 2001, but it is hard to see him taking a step backwards at this point in career.

Marcus Ericsson's only chance of driving in F1 next year is by continuing with Sauber and he still enjoys strong ties with the team's owners. He is likely to be in direct competition with Ferrari reserve Antonio Giovinazzi, the Italian driver who deputised for the injured Pascal Wehrlein at two races last season. His nationality makes him another natural fit with Alfa and, if Leclerc stayed put, would see Sauber become a fully-fledged Ferrari junior team. Of course if Leclerc does make the step up to the Maranello outfit, Giovinazzi and Ericsson may well be teammates in 2019.