GRANOLLERS, Spain (AP) Lewis Hamilton will be looking for his fourth win of the season at this weekend's Spanish Grand Prix, and it will be hard to stop the defending world champion if he gets another pole position on a Catalunya track where overtaking is notoriously difficult.
Eighteen of 24 races here have been won from pole, and Hamilton has started from pole in all four races this season. The only hiccup in an otherwise perfect campaign was when four-time world champion Sebastian Vettel beat him at the Malaysian GP, with Hamilton finishing second.
Hamilton leads his Mercedes teammate Nico Rosberg by 27 points and Vettel by 28. Rosberg, who pushed Hamilton all the way in last year's championship, is growing increasingly frustrated after a run of one win in the past 15 races.
The German driver will need strong performances in Spain and at the Monaco GP in two weeks' time - where he won last year - to put some pressure on Hamilton, who won the Spanish GP for the first time last year. Rosberg also needs to fend off the growing threat from Vettel and his Ferrari teammate Kimi Raikkonen, who roared back to form with a brilliant second-place finish at last month's Bahrain GP.
''I'm feeling really fired up for the next races, knowing I have all the tools available to me for a strong performance,'' said Rosberg, who finished third in Bahrain after sustaining a late brake problem. ''I can't wait to get back out there in Barcelona.''
If Rosberg fails to secure pole position, and Hamilton does, the German driver's best chance will be to attack on the long run up to the first turn.
The Catalunya track - which puts great strain on the chassis and power unit - is arguably even more difficult to overtake on than Monaco's tight and sinewy circuit.
''The circuit itself really tests every element of the car, especially the aero(dynamics) so it will be interesting to see how each team has developed and also to see who has brought the most upgrades since the last race,'' Rosberg said. ''I know our guys have been working mega hard at the factory, so let's see what we've got.''
Mercedes' engineers have good reason to keep working.
Ferrari has come back strongly after failing to win a race last year for the first time in two decades. Vettel has managed a podium in every race, and the gap is closing in terms of race speed. Ferrari's car is also softer on the tires than the Mercedes, giving it a slight edge in durability during a long race.
''In 2014, we had a lead of over 100 points in the constructors' championship. This year, it's 52 points and we are in a close battle at every race weekend,'' Mercedes' head of motorsport Toto Wolff said. ''Every single team member knows that we can't afford to take our foot off the gas so we are pushing hard with developments.''
Hamilton and Rosberg fell out at times last season and Mercedes can ill-afford any feuding, with Ferrari pushing hard. Still, team management has not intervened by nominating No. 1 and No. 2 drivers, so they are still free to compete with each other.
''Lewis is in the zone right now, probably driving as well as he has ever done, and Nico showed his teeth in Bahrain with some forceful overtaking and a strong, aggressive race,'' Wolff said. ''We're expecting more of the same in Spain.''
Spanish fans are unlikely to have much to cheer about on Sunday. Home favorite Fernando Alonso has yet to score a point since leaving Ferrari to join McLaren, which has been beset by reliability problems since switching to Honda engines.
Alonso, a two-time world champion, last won a race in 2013 - on the same circuit.
Red Bull, the dominant team in F1 from 2010-2013 when Vettel won four straight titles, also needs to improve after a series of spectacular engine blow outs.
Australian driver Daniel Ricciardo has already used three of his four allocated engines for the season, and teammate Daniel Kvyat is also struggling, as are both Toro Rosso drivers. Renault is the engine supplier for both teams.
''(The first four races were) far from where we expected to be and ultimately disappointing,'' Red Bull tram principal Christian Horner said. ''We can see on the engine side that Renault are making some steps forward as well.''