There is a saying in Formula One that it is easier to make a quick car reliable than it is to make a reliable car quick.
Championship leaders Mercedes find themselves in the first and better of those two conditions at the moment. The W05 is quick: fast enough to win nine of the eleven races so far, and reliable enough that more than half of those saw both its cars fill the top two places.
But the fact remains that as the season has gone on more problems have surfaced with their design, and that has opened doors for their rivals. But as F1 returns to action in Belgium this weekend the team is under no illusions that their persistent gremlins are taking the shine off an otherwise dominant performance.
"Looking ahead to Spa, and also reflecting on our recent performances, it is clear that reliability must be a key focus for the team if we are to maintain the hard-earned advantage established in the opening stages of the year," said the team's motorsport director Toto Wolff.
"Although the team has done a fantastic job, we are fully aware that this championship is far from decided - as demonstrated clearly in Hungary by the performance of some of our competitors."
Hungary was the latest in a series of race weekends which did not go entirely to plan for Mercedes. For the second event in a row, Lewis Hamilton found himself starting from the back of the field due to a problem in qualifying - this time a turbo fire. It left him mounting a recovery drive during the race, and although third place was a superb result under the circumstances, for the first time this year Mercedes were beaten by two of their rivals - Red Bull and Ferrari.
Williams expect to be strong
However another of their closest competitors pose a greater threat this weekend: Williams. The FW36 chassis, which also uses Mercedes' superb PU106A hybrid power unit, excels on circuits with long straights which reward its aerodynamic efficiency. This weekend's race at Spa, and the next round at Monza on an even faster track, represent their best chance of victory this year.
"Spa is a circuit that should suit us," acknowledged the team's head of vehicle performance Rob Smedley, "there is very high drag and engine sensitivity and those features will benefit us".
So while the Mercedes duo offer less than compelling odds for victory - 1.75 for Hamilton, 2.40 for Nico Rosberg - the Williams drivers are far better value. Valtteri Bottas has had the beating of team mate Felipe Massa so far, so his odds are quite a bit shorter at 18.00 versus Massa's 31.00. Massa has won the Belgian Grand Prix before, of course, though it came after 'on the road' winner Hamilton was controversially penalised. The pair have similar odds for qualifying as well. Keeping in mind Spa's dependably capricious climate, and recalling how Bottas took a superb third on the grid during a rain-hit qualifying session in Canada last year, he looks particularly good value for pole position.
Raikkonen is the Spa master
Spa is renowned as a true test of driving skill and the most successful driver at the circuit who is currently racing is four-time Belgian Grand Prix winner Kimi Raikkonen.
He's had a hard time since returning to Ferrari this year but there were clear signs of progress in Hungary, where he scored a season-best sixth despite a compromised starting position due to his team's tactical error in qualifying. Odds of 15.00 for a podium finish are worth considering.
Keith Collantine is the editor of Formula One blog F1 Fanatic.