The summer break in the Formula 1 calendar gives teams and drivers time to pause and fine-tune their strategies for the final nine races of the season.

The drivers' title is going to be an enthralling three-way battle between Mercedes team-mates Lewis Hamilton and Nico Rosberg, along with Sebastian Vettel, all the way (at least hopefully) to the end of November.

Between them, that trio has won all 10 Grand Prix so far in 2015 and they have filled the podium places in six of those races. Hamilton has won half of the GPs to date, but he only leads Rosberg by 21 points, with the same distance again to Vettel.

With so many points still to play for, Hamilton knows he hasn't got an unassailable lead, especially as he was in a worse position than Rosberg at a later stage of the season 12 months ago before going on to become world champion for the second time.

Here, we look at three races which could play a crucial role in determining who wins this year's title:

Belgium

Given what happened in Belgium last year, the first Grand Prix after the summer recess is a race you can't miss. The simmering feud between Hamilton and Rosberg boiled over in the most spectacular fashion as the latter was accused of deliberately crashing into his team-mate early in the race. Hamilton was eventually forced to retire and Rosberg's second place allowed the German to open up a 29-point lead in the drivers' standings. A repeat this year will certainly not leave Hamilton playing catch-up in such a dramatic fashion, or see him lose his place as the favourite with online bookmakers, but the Briton will have to be wary of any past emotions coming to the surface. Vettel, though, can't be discounted as he won at Spa in 2011 and 2013, and he will be poised to pick up any pieces if the red mist descends on the Mercedes team again.

Russia

Hamilton led all the way in the first running of the Russian GP at Sochi last year after qualifying on pole, but it was another race not without incident. Rosberg locked his front wheels when trying to challenge Hamilton on the first lap and he was forced to pit before eventually coming through the field to take second. Vettel, meanwhile, endured a horrendous weekend with his car as he qualified down in eleventh before finishing eighth in the race. With the long pit lane, and a one-stop strategy likely to be in place, the performance of the pit crews could also play a key role in who comes out on top.

Mexico

The Formula 1 circuit returns to Mexico for the first time since 1992 and the drivers will be hoping the Hermanos Rodriguez track holds up. When F1 racing was previously staged at the venue in the late 1980s and early 1990s, the track was notoriously bumpy and caused numerous tyre problems and crashes. The track has been resurfaced ahead of F1's return and the Peraltada has also been modified to be a less severe right-hander at the end of a lap. Given the course's history, it hasn't always paid to take risks, which could be to the detriment of the two drivers chasing the leader in the standings. It's also going to be the case of which driver is the quickest learner and, with just two races after Mexico, the outcome could be decisive.