As the Formula 1 season restarts in Europe, some crucial questions could be answered in the battle for the drivers’ championship. Entering this weekend’s Spanish Grand Prix we may be about to discover just how active the title fight will be in 2015.

After the first Grand Prix of the year, it appeared that the race to be crowned champions would be more of a procession. Champions Lewis Hamilton was in a league of his own, with his Mercedes a class apart and teammate Nico Rosberg seemingly beaten into submission after falling away in last season’s acrimonious title battle. But two weeks later Ferrari and their new talisman Sebastian Vettel threw a major spanner in the works in Malaysia when the four-time world champion with Red Bull took the checkered flag in just his second race for the Scuderia. It was no freak result either, with Ferrari having made huge steps forward. While Hamilton claimed victory in the next two races in China and Bahrain, Ferrari were again in contention. Following the example set by his teammate, Kimi Raikkonen split the Mercedes pair last time out.

After a three week break, Ferrari hope to have made further improvements going into the Spanish Grand Prix. Yet Vettel has consistently downplayed the extent to which the gulf between his team and Mercedes is being eaten away. After finishing four tenths of a second behind Hamilton in Friday’s second practice at the Circuit de Catalunya, Vettel continued the theme. “I think we can improve the cars, but the gap with Mercedes is still there,” he said, according to

In terms of single-lap pace, Vettel looks to be right. Hamilton has taken pole position in each of the four Grand Prix this year and Friday’s results suggest that he is a strongly positioned to do so again this weekend. But Ferrari’s strength so far has been over race distance and specifically, as they showed in Malaysia, in managing tire wear in the heat. While it won’t be nearly as hot in Barcelona on Sunday as it was in Sepang, it could still be telling.

Of course Mercedes have also had time to make improvements, and Hamilton is anticipating that, while not large in number, they could make a significant difference.

“I feel confident that the team have done everything they could and that they can do to be as strong as they can this weekend and to improve,” Hamilton said ahead of practice in Spain, reports Reuters. “I think others will have improved as well but I’m confident in my guys. We’ve not come with a ton of's generally not the philosophy of the team to just pile on lots of different things. We’ve come with quality upgrades rather than quantity.”

Despite Mercedes’ advantage over a single lap, Hamilton’s teammate has failed to impress in qualifying so far. Not only has Rosberg been unable to match the pace of the man with whom he shares a garage, but in two of the last three races he has also qualified behind Vettel. After letting a lead slip to lose out on the drivers’ championship last year, Rosberg badly needs to alter the perception that he is now going to slip into a role of the de facto No. 2 at Mercedes. Now would be a good place to start, given that it was in the European swing where the German won three races last season. After topping the timing charts in Friday’s morning practice but trailing Hamilton and Vettel in the afternoon, Rosberg conceded that he needed to make adjustments in order to get the edge in qualifying.

“On one lap I still have a bit of work to do to find some more speed, so I'll be working hard with the team tonight to find out where I can improve,” he said, reports

Rosberg still leads Vettel by a single point in the driver’ standings, but, with Hamilton having amassed a 27-point advantage, the two compatriots will be eager to show in Spain that they can make the 2015 title race far more intriguing than many imagined.