Mark Thompson/Getty Images
The top step may be out of Vettel's reach
It's not just the obvious threat of Spa expert Kimi Raikkonen or Hungarian Grand Prix victor Lewis Hamilton that Vettel will need to keep his eye on.
2013 is becoming wonderfully more open as the season progresses.
A determined Mark Webber—who despite the best efforts of conspiracy theorists does have access to the best car—will be more focused than ever to return to winning ways ahead of his sports car switch in 2014.
You've then got Nico Rosberg, twice a winner so far this season, to factor in as well.
The German's come of age this year alongside Hamilton and is exceeding many people's expectations. Don't count him out of the pole or win battle this weekend.
It'd also be foolish to write off Fernando Alonso, despite the Spaniard's summertime troubles with Ferrari. Then there's Romain Grosjean, who has been knocking on the door of his first win in the last two races.
Jenson Button could also be a factor. The McLaren is not on a par with the other cars, but the Briton loves the circuit, having won there in 2012, and the team is improving its understanding even if development has stopped.
What that means is we have a perfect melting pot for F1 to resume in.
Sebastian Vettel's only victory at Spa came in his all-conquering 2011 season. He will not have it so easy this time around.