SPA-FRANCORCHAMPS, Belgium, Aug 26, 2011 (AFP) - Defending world champion and current series leader Sebastian Vettel was left moaning in the rain on Friday after struggling in practice for Sunday's Belgian Grand Prix.
The 24-year-old German was down in 10th place for Red Bull while his team-mate Australian Mark Webber was the fastest man - a clear signal for the champion that his easy early-season supremacy is over.
Vettel, who won five of the opening six races, has won only one of the last five and none of the last three and appeared reconciled to another difficult weekend in the Belgian Ardennes.
"I think I learned as much as you did today," he told reporters after the sessions. "It was quite tricky because the weather changed all the time and it is a shame in wet conditions that we only have one free set of inters (tyres). "For the rest of the weekend you can imagine the weather forecast. The rain is absolutely possible, the question is how much?"
Many of the paddock's most seasoned observers believe Vettel has now reached the position in which - despite a massive points lead in the title race - he feels vulnerable to attack and he is weighing up his strategic options: to defend, or to attack.
Showing none of his trademark light humour and irony, Vettel said he had managed only one lap in dry conditions. He was clearly frustrated while other drivers, who revel in the wet weather, appeared to be more relaxed.
"We had a little bit of running in the dry," he added. "On the front wing we got a decent result on that, but that was the only run we had in dry conditions. "Lap times are difficult to judge today, and difficult to know where we are, but the car feels okay. Let's see what we can do."
Webber, who celebrates his 35th birthday on Saturday, topped the times for Red Bull with some ease. The Australian, who is the only man among the leading drivers still without a win this year, clocked a fastest time of one minute and 50.321 seconds to outstrip nearest rival Fernando Alonso of Ferrari by one-tenth of a second.
Two-times champion Spaniard Alonso was one of several men to trade fastest laps with Webber along with Vettel and McLaren's Briton Jenson Button. Seven-times champion German Michael Schumacher, 42, had topped the times in the morning's opening session for Mercedes, marking the 20th anniversary of his Formula One debut with a flourish.
But in the afternoon he was down in 11th, five places behind his Mercedes team-mate compatriot Nico Rosberg, while Vettel wound up 10th.