Red Bull dominated Friday’s second practice session for the Belgian Grand Prix as they left the rest of the field trailing by close to a second. Championship leader Sebastian Vettel was under a tenth of a second quicker than teammate Mark Webber in the afternoon, with Lotus’s Romain Grosjean 0.8 seconds behind.

Vettel is looking to extend his 38 point lead in the drivers’ standings this weekend at the famed Spa-Francorchamps circuit. Much of the attention, though, has been on the identity of his teammate for next year. Webber has long-since announced that he will be retiring at this season’s end, which has left a hotly desired vacancy at a team which is set to win its fourth consecutive constructors’ title this season.

Lotus’s Kimi Raikkonen, currently second to Vettel in this year’s championship, was hotly tipped to fill the role before his manager ruled out the switch this week. Red Bull boss Christian Horner, though, has said that the Finnish former world champion remains in the running. Daniel Ricciardo, currently at Red Bull’s junior team, Toro Rosso, appears to be the other leading candidate.

The musical chairs ahead of the new season promises to be an intriguing subplot to the Grand Prix at one of the world’s great circuits. Worryingly, also set to be on the agenda is once again a debate over tire safety. Pirelli introduced redeveloped tires after a series of punctures at the British Grand Prix in June. But in practice in Belgium on Friday both Vettel and Ferrari’s Fernando Alonso suffered tire failures. Pirelli have called the situation “a worry,” while Vettel is eager to find out what happened.

"We don’t know what happened when I got the puncture in P2,” he said, according to the official Formula One website. “We lost the rear right, very suddenly, so we need to have a look -- Pirelli is working on finding out why it happened.”

While Vettel was left to reflect on a “positive day” overall, the same was not true of his title rival Lewis Hamilton. After taking his first victory for Mercedes at the last race before the summer break in Hungary four weeks ago, Hamilton was 12th in second practice and conceded that improvements are necessary if he is to be able to challenge for the front grid positions in Saturday’s qualifying.

“It hasn't been a good day generally. I still feel cool but I've been struggling,” he told Sky Sports News. “The car doesn't feel the same as it did in the last race, that's obvious because we have less downforce this weekend. We've got some work to do tonight."

Ferrari’s Felipe Massa was fourth fastest ahead of Toro Rosso’s Jean-Eric Vergne and Raikkonen. Alonso, who was quickest in a rain-affected morning session, was sixth in the afternoon. Rain may again strike to add an element of predictability to qualifying.

Where to watch: Qualifying for the Formula One Belgium Grand Prix will get underway at 8 a.m. ET. A live stream will be available on NBC Sports Live Extra, while it will be shown in delayed form on NBCSN at 12.30 p.m.