MELBOURNE, Australia - Mark Webber will be the oldest driver on the Formula 1 grid at his home 2013 Australian F1 GP this weekend (March 15-17)) but suggestions he is reaching the end of the road sound premature to Red Bull team principal Christian Horner.Horner said: "The last three years have apparently been Mark's 'last year' yet he has been retained by the team because of what he is doing in the car."There are an awful lot of drivers who would like to be in a Red Bull car but he's there on merit. While he delivers for the team he will have that place."MENTAL HEALTHWebber will be 37 in August and out of contract with Red Bull at the end of 2013 after agreeing to the latest in a series of one-year extensions. Speculation about his future is inevitable.The Australian, who has never won his home race, came close to taking the championship in 2010 but lost out to German team mate Sebastian Vettel who is now, at only 25 years old, the youngest triple champion.Red Bull adviser Helmut Marko caused a stir earlier in 2913 when he questioned Webber's mental strength and suggested he was a driver who could be unbeatable a couple of times a year but struggled to maintain a title challenge.Horner continueds: "The difficulty for Mark is that he is constantly judged against a young man in the other car who has achieved so much. What he (Vettel) has done in just over 100 races, with 25 victories, three-time World champion, youngest points scorer, pole winner, race winner, champion, is remarkable."He's being constantly measured against a driver that is, in my view, the best of a generation, and that makes it harder for Mark."The Red Bull seat, with a team that has won the Constructors' title for the previous three years, is one of the most coveted in the sport. There are plenty of candidates eyeing it up, among them Australian Daniel Ricciardo and Frenchman Jean-Eric Vergne who drive for the Red Bull-owned Toro Rosso junior team and might be expected to graduate to the senior outfit.'NEEDS A CAMPAIGN'Horner said Red Bull wanted the strongest drivers it could get. "We're very happy with Mark going into what will be his seventh year with the team, the fifth consecutive year he will have been paired with Sebastian."Mark has demonstrated that on his day he can be unbeatable but he does just need to string a campaign together. He's improved as he's matured. Last year he drove very well."If we didn't think he could still do it then we wouldn't have taken him for another year." Stay with Wheels24 for the 2013 Formula 1 season – fresh reports every day.