Malaysia preview - Alonso's return steals the spotlight

Sweltering heat and the threat of rain could throw up a few surprises as Formula One racing heads to Malaysia for the second round of the 2015 championship. Ahead of the weekend though, the focus has centred firmly on racing returns - particularly that of McLaren's Fernando Alonso...

The Spaniard isn't the only one preparing to make his 2015 race bow at Sepang - Valtteri Bottas will return to active duty after missing the season opener in Australia, while Marussia are confident they have resolved the software issues that consigned them to the garage throughout the Melbourne weekend.

But Alonso naturally attracts the spotlight given both his stature and the circumstances surrounding his crash during the first pre-season test in Barcelona on February 22.

More than a month has now passed since he sustained a concussion in the incident, and in those intervening weeks he has maintained his usual fitness regime and also undertaken a separate neurological programme closely monitored by leading sports scientists which was designed to ensure that he is fully recovered and that it is safe for him to race again.

He's also spent a lot of time at the McLaren factory, discussing the car and the incident with his engineers, and after recalling a feeling of heaviness in the steering just prior to going off the track, both his and Jenson Button's cars have been fitted with extra sensors in that area ahead of this weekend's race.

All that remained was for him to pass a mandatory comparison test with the FIA - which was duly completed on Thursday morning. Each year a driver undertakes a pre-season assessment against which further input can subsequently be measured if he sustains a head injury. In this way the medics can determine if there has been any adverse change in his baseline coordination. After passing the test, Alonso was given the all clear to compete.

The 33 year-old says he is expecting a tough weekend, after the performance of the McLaren-Honda package in Melbourne.

"I watched the weekend in Australia very closely and I was in touch with the team from the moment they arrived. It's clear we have a lot of work ahead of us but Jenson's result in Melbourne was encouraging from the point of view of reliability and data collection, which are extremely important."

Meanwhile, down at Williams Bottas is confident he will be able to drive after he tore an annular disc in his lower back during qualifying in Albert Park.

"As always, Malaysia is a very hot and humid race, and although these aren't the ideal conditions for the car we have had some exciting races in Sepang over the years," the Finn says. "There is also always a risk of rain which we have to be aware of, but it brings some more spice in the suspense.

"After Melbourne I stayed in Asia to acclimatise to the hot conditions and adjust to the right time zone. I trained a lot over the winter to prepare for these physically difficult conditions. After such a frustrating Sunday in Australia, I have taken the necessary measures to make sure I arrive in Malaysia fit to race and ready to bring the results home."

Over at Marussia, team principal John Booth believes that the revived team will be in much better condition to put on a decent show after problems integrating 2014 and 2015 software kept the MR04s in the garage in Australia.

"After the disappointment of not meeting our objectives there, we head to Malaysia this week hoping for a more typical race weekend," he said.

"We headed back to the UK to regroup technically and bolster the work we had completed in the field in Melbourne, and as a result we are in a different position to the one we were in two weeks ago. Again, the rate at which we are progressing, when one takes into account our circumstances pre-season, is very impressive and everyone in the team is to be commended on a huge continued effort. Sepang always throws up its own unique challenges, thanks to the combination of fierce heat and a well-timed downpour, but we look forward to debuting the car and our two young drivers and to finally start getting down to business on the racetrack."

Sepang is very hard on tyres, so Pirelli's hard and medium compounds will play key roles in the developing story. The combination of an abrasive surface, high g-loadings through the fast, open curves, high heat and high humidity can be debilitating.

"The Australian Grand Prix two weeks ago confirmed what we saw in testing: lap times that are two seconds or more faster this year compared to last year, in every session," says motorsport director Paul Hembery.

"This exponentially increases the workload on the tyres: something that will be particularly in evidence at Sepang, which has some of the most abrasive asphalt we race on all year and a number of fast corners that take a lot of energy out of the tyres. For all these reasons, we have chosen the two hardest tyres in our range this weekend: P Zero Orange hard and P Zero White medium, as has always been the case in Malaysia.

"We should see a return to at least two stops per car in Malaysia - perhaps more if the weather gets in the way - after an early safety car meant that unusually most drivers stopped only once in Australia. Wear and degradation is traditionally very high in Sepang, so managing the tyres and the strategy carefully will be key to success."

Teams will also have to throw the weather into the mix, with current forecasts suggesting a high chance of rain late in the afternoon on every day of the weekend, Sunday in particular.

The fact the showers are often daily only exacerbates the headaches for teams and drivers to contend with, as the rubber that gets laid down in each session tends to get washed away overnight, making the pattern of track evolution quite hard to predict. Standing water can also be a feature of wet races and judging the crossover point between full wets and intermediates can also have a crucial effect on the result.

So while Mercedes are the obvious early favourites ahead of the weekend, the likes of Ferrari and Williams will be in the hunt and determined to turn any volatility to their advantage.

As was the case last year, the track will feature two DRS zones. The first zone has a detection point 54 metres after Turn 12 and an activation point 104 metres after Turn 14, whilst the second has a detection point 16 metres after Turn 15 with the activation 28 metres after the same corner.

Even with the threat of rain, the weekend is forecast to be extremely humid, with temperature highs ranging from 38 degrees Celsius on Friday to 35 on Sunday. The race will start at 1500 local time (0700 GMT) - an hour earlier than in 2014 - and will run over 56 laps or 310.408 kilometres (192.887 miles).