By Alan Baldwin
LONDON (Reuters) - The 'toughest decision' of Daniel Ricciardo's life, in opting to leave Red Bull and join Renault (PA:RENA) next season, could be good news for some Formula One drivers but leaves others facing an uncertain future.
The immediate questions to be answered are who will be the Australian's replacement alongside Max Verstappen and what will happen to Spaniard Carlos Sainz, whose place he has taken?
The two go together, with 23-year-old Sainz loaned to Renault by Red Bull for 2018 after the French manufacturer needed a replacement for under-performing Briton Jolyon Palmer.
Sainz could slot in at Red Bull but the previous pairing of him and Verstappen at Toro Rosso was far from smooth and the Dutch 20-year-old is now the senior team's clear focus.
French rookie and 2016 GP2 champion Pierre Gasly has meanwhile impressed at Toro Rosso and, with previous experience racing for Red Bull's new for 2019 engine partners Honda, could be in line for a promotion.
Until Red Bull decide, Sainz's hands are tied and any other move -- and McLaren have expressed interest -- must remain on hold.
Gasly's promotion would leave Red Bull with a headache at Toro Rosso, with no as-yet qualified youngster seemingly in a position to step in from the ranks of Red Bull junior drivers and Sainz unlikely to return there.
That could mean Gasly's 2018 team mate, New Zealander Brendon Hartley, gets a reprieve just as the exit door had appeared to be opening.
McLaren are meanwhile waiting to see what double world champion and Le Mans 24 Hours winner Fernando Alonso, now 37, decides to do next.
That big decision will also affect the futures of struggling Belgian team mate Stoffel Vandoorne and up-and-coming British reserve Lando Norris.
Toro Rosso expressed an interest in Norris when a replacement for Hartley was mooted earlier in the season but McLaren did not play ball.
Whether that might change if there is no 2019 seat at Woking available remains to be seen.
KNOCK-ON EFFECT
Renault's surprise signing of Ricciardo, which came as almost everyone in Formula One assumed his staying at Red Bull was a done deal, also has a knock-on effect on the plans of Mercedes, Force India and Williams.
Force India are in administration with their future uncertain.
It had been widely assumed that the team's Mercedes-backed French driver Esteban Ocon was bound for Renault.
The speculation was that Canadian Lance Stroll was in turn poised to switch from Williams, bringing also some sort of investment from his billionaire father.
The vacancy at Williams could then have gone to another Mercedes protege and Formula Two leader George Russell, whose route now looks less certain -- unless Force India's Mexican driver Sergio Perez also moves.
There could also be openings at U.S.-owned Haas, with Frenchman Romain Grosjean having an erratic and costly season, and at Sauber where Monegasque rookie Charles Leclerc is tipped to replace Kimi Raikkonen at Ferrari (NYSE:RACE).
The Finn could then become another player in the game of musical chairs.
Once that is all decided only time will tell whether Ricciardo has made the right move, as four-times world champion Lewis Hamilton did at the end of 2012 when he left McLaren for as-yet unsuccessful Mercedes.
Formula One has plenty to contemplate and speculate about as the August break starts and the 'silly season' shows no sign of abating.