Victory in the Singapore Grand Prix two weeks ago put Lewis Hamilton in the lead of the Formula One drivers' championship for only the second time this year.
But with a narrow three-point lead over team mate Nico Rosberg, and 150 points still up for grabs over the final six rounds, the fight for the championship remains wide open. Lewis Hamilton is the favourite to win on 1.70, Nico Rosberg 3.00, and if you think Red Bull's Daniel Ricciardo can pull off a major shock he is on odds of 12.00
But while Hamilton may have won at Singapore the race also indicated Mercedes' rivals are getting ever closer to them. At the end of Saturday's qualifying session Red Bull and Ferrari were just 0.17 and 0.23 seconds slower than the W05s around a 105-second lap of the Marina Bay circuit - one of their most competitive showings of the season so far.
Red Bull in particular have made steady progress with their RB10. Most surprisingly, given their torrid start to the year in pre-season testing, the RB10 has been more reliable than Mercedes' W05 of late - and the silver car ran like a train in testing.
Sebastian Vettel's fearsome form at the Suzuka circuit makes him one to watch in this weekend's Japanese Grand Prix regardless of the conditions. What the weather does is going to be one of the keys to this weekend's race.
Extreme conditions are far from unusual in Japan - qualifying sessions at Suzuka had to be postponed in 2004 and 2010 due to very heavy rain. Ahead of this weekend's race there are fears Tropical Storm Phanfone could cause a similar level of disruption.
The prospect of rain on Sunday is a growing threat, and that will be welcome news for Red Bull, whose car thrives in these kinds of adverse conditions. It may also offer an opportunity for Vettel, who has won this race four times and never failed to finish on the podium at Suzuka, to claim his first win of the season. Otherwise he could be heading for the first win-less full season campaign of his career.
If the weather forecast continues to deteriorate Vettel's odds of 12.00 to win will look like increasingly good value. So will team mate Ricciardo, already a three-times winner this year, on 9.00
2015 drivers championship
Fernando Alonso's future is a point of intense speculation within Formula One at the moment. Rumours suggest he may cut short his Ferrari contract. which is due to run until 2016, out of frustration at the lack of success in the five years since he joined the team.
With that in mind, it is interesting to note his odds of championship success next year are 8.00. Whether you expect him to stay at Ferrari next season or gamble on a return to former team McLaren and their new Honda engines, now could be the chance to scoop up some unusually long odds on one of the sport's most relentlessly competitive drivers.
And given how impressive Daniel Ricciardo's season has been this year, odds of 12.00 on him taking next year's title also look quite appealing - and are twice as long as Vettel's on 5.00.
But for this year the championship contest is all about the Mercedes pair. The team could wrap up the constructors' championship in Japan this weekend. Once they do that the gloves will be well and truly off between their two racers in the fight for the drivers' title.
Keith Collantine is the editor of Formula One blog F1 Fanatic