Former F1 winner Heinz-Harald Frentzen has said it will be difficult for Sebastian Vettel's rivals to chase down his championship advantage in 2011.
"At the moment they (Red Bull) can only defeat themselves," he told the Austrian portal laola1.
"They have the best car even if their best innovations are now elsewhere (also on rival cars)," said the 44-year-old German, who is now an occasional third steward at grands prix.
Frentzen, who won races with Williams and Jordan and most recently drove for Sauber in 2003, also commented on suggestions F1 has become too complicated in the new era with the DRS system and heavily degrading tyres.
Sebastian only has to score points regularly to win
"No matter how it is in F1, there is always criticism," he said.
"In the past people always complained that there is not enough overtaking, now there is much more and yet still everybody is unable to agree."