Sebastian Vettel needs to rediscover his speed in qualifying if he is to protect his overall Formula One lead at the Monaco Grand Prix.

Monaco is the hardest track to overtake on in F1, with only two drivers winning from outside of pole position in the last 10 years, so starting from the front is crucial.

But Vettel's Red Bull has not been as dominant in qualifying over the last three races, and the German's lead over Lotus driver Kimi Raikkonen is just four points going into Sunday's showcase race. With Ferrari's Fernando Alonso also closing the gap after his victory at the Spanish GP two weeks ago, Vettel is under pressure to deliver his third pole of the season.

Red Bull has won the past three Monaco GPs — all from pole position — with Mark Webber winning two, and Vettel triumphing in 2011. But Vettel's last pole was four races ago in Malaysia and he was below-par Thursday in two practice runs, finishing 10th and ninth.

"I would say that it is hard for us to say where we are right now," Vettel said. "The good news is that we have a fast car when everything comes together. Now it is up to us to make everything come together."

Mercedes has taken pole position for the past three races.

Tire management has been a crucial factor, with the Pirelli tires shredding too easily in all five races so far. The Italian manufacturer was heavily criticized in Barcelona, where there were nearly 80 pit stops and most drivers had to shelve plans for a three-stop strategy, taking four instead.

"When the majority of the drivers are struggling, it means that you cannot drive as you are used to," said Vettel, who has been one of the most outspoken drivers on this issue. "If your only focus is the tires, then that is not racing any longer in the way that we knew."

Ferrari has managed its tires far better and it showed in Barcelona, where Felipe Massa finished third behind Raikkonen's Lotus. Both Ferraris beat the Red Bulls — with Vettel finishing fourth ahead of Webber.

Lotus has largely managed its tires well — Raikkonen did three stops in Spain — but lacks pace. Raikkonen qualified second for the Chinese GP but otherwise has been no higher than fourth on the grid, and as low as 10th.

"We've still got a few other areas to improve," the Finn said. "To get pole we have to make the car a bit faster overall and I have to drive a bit better, then we'll have to see what happens."

Monaco is likely to be no more than a two-stop race, and some teams might gamble on one, because it is almost impossible to recover a lost position on the narrow street circuit. That means teams will have to balance saving tires on Saturday with the need for qualifying speed.

"To be honest, we haven't had a shot at how to go about qualifying on Saturday," Vettel said. "(But) this is Red Bull and we've always found an answer to the toughest challenge."

Alonso has moved up to third overall and cut Vettel's lead to 17 points, and there has been some talk that perhaps Vettel is not so dominant this season.

"Two wins in five races. Doesn't that sound good?" Vettel said. "Even the races with a third and two fourth places have been a success, given our abilities in that very moment."

Sunday could finally see Mercedes winning a race. Rosberg is looking for his third straight pole, while Hamilton started from pole three races ago in China.

But while Hamilton has managed two third places, Rosberg has not finished higher than fourth. Mercedes has not yet found the durability to go with its speed, despite both drivers doing more laps than others in practice.

"I can understand that people make out Mercedes as the favorite here," Vettel said. "It will again be a question of the tires — how long they last — because a pit stop will put you way back and overtaking is practically impossible."

Vettel is a big fan of Monaco, which blends danger with a picturesque setting featuring the glittering harbor, the resplendent casino and Prince Albert's palatial residence looming imperiously over the track.

"In terms of excitement nothing beats the Casino part," Vettel said. "You arrive in this left-right passage with quite some speed and you arrive there in seventh gear, flying blind."