Fernando Alonso's consistency an 'annoyance' to Red Bull, says Christian Horner

Sebastian Vettel delivered a crucial victory in the Singapore Grand Prix to close the gap to Alonso in the championship battle to just 29 points.

However, Alonso recovered from another difficult weekend to finish third and maintain an impressive run of podium finishes that have helped him head the title chase for much of the campaign.

Red Bull team principal Christian Horner believes that Vettel is in the form of his career at the moment - but that it is Ferrari's lead driver who is making their life too difficult.

"Seb has the benefit of experience now," explained Horner when asked if Vettel was stronger because of the up-and-down campaign he has endured this year.

"He has never given up; he has had some adversity thrown at him. I have never seen him as focused going into a GP as he was in Singapore.

"He executed a very impressive race. For the championship it is wide open, but it is annoying that Fernando keeps popping up on a podium at the end of a grand prix."

Horner believes that as many as six drivers still have a chance of winning the championship - and that Red Bull's hopes pretty much rest on Alonso being shunted off the podium by other cars.

"In 2010, Seb was 25 points down with two races to go so it demonstrates that anything is possible for any of the drivers," he said.

"We have had bad luck on occasions this year; we have had strong races, and we are working hard to develop the car at each of the remaining races.

"We will keep on pushing, but we need to keep taking points off Fernando - and that means getting a few more cars between us and him."