Nico Rosberg followed up his win at the first Formula One Grand Prix of the season by setting the fastest time in Friday’s practice in Malaysia, but Mercedes’ rivals look to have closed the gap since Australia.

Mercedes had a half-second advantage in practice in Melbourne as they backed up their superiority throughout winter testing. But ahead of the second race of the season in Kuala Lumpur, Ferrari’s Kimi Raikkonen and Red Bull’s Sebastian Vettel were both within a tenth of Rosberg. The second Silver Arrows of Lewis Hamilton, who went fastest in the morning, recorded the fourth quickest time. Rosberg conceded that the gap appears to have lessened, but was more concerned about the battering his cars’ tires were taking in the blazing heat on the Sepang ciruit.

“The quickest teams seem to be closer together than in Australia, so we still have work to do overnight to improve our level of performance,” he said, according to the official Formula One website.

"It was crazy conditions out there,” he added. “In the very, very warm temperatures, it's a huge challenge to get everything right. The cars are on the edge and the tire degradation was higher than expected today.”

While it is anticipated that Mercedes have been holding something back so far, their rivals can still be delighted with their progress. Raikkonen had looked ill at ease thus far in his new Ferrari F14 and was handsomely eclipsed by teammate Fernando Alonso, who was only fifth in practice in Malaysia, in every session in Australia. Thus, the Finn was understandably pleased with his improved showing.

"This was definitely a positive day and I had a better feeling compared to Friday in Melbourne,” he explained. “I was more comfortable with the F14 T today and even if we had no problems whatsoever, we know there's still a long way to go and a lot to do.”

After a torrid winter, Red Bull surprised many with their performance in Australia. A second place for Daniel Ricciardo, which was later taken away for exceeding the permitted fuel usage -- a decision that the team is appealing -- and they appear to have taken another step forward in the intervening two weeks.

“We are more or less there in terms of pace, which is very good news," Vettel said, reports BBC Sport. "For everything else we have to be patient. It is still early days, we still have a lot of problems we need to solve.

"But when we get the package together we seem to be on the right page, so I'm looking forward to tomorrow and Sunday.”

The day was not so encouraging, though, for McLaren. Kevin Magnussen took second place in his debut Grand Prix in Australia, with teammate Jenson Button also getting on the podium, but they found themselves down in 12th and ninth place, respectively, on Friday afternoon.

"We're finding it tough out there today -- especially in the heat,” Button said. “We're not as strong as we'd like to be in high-speed corners -- and, when you have downforce issues, they're further amplified by the hot weather. So our long runs were tricky, in terms of both tire degradation and outright pace.”

Where to watch: Qualifying for the Malaysian Formula One Grand Prix will get underway at 4 a.m. ET. Coverage will be provided by NBCSN, with a live stream provided by NBC Sports Live Extra.