MONTREAL, Canada - Sebastian Vettel is a long way from the top of his game and is still improving as both a competitor and driver, according to Red Bull team chief Christian Horner.As the dust settled in the aftermath of the Canadian Grand Prix dominated by Vettel but over-shadowed by the death of a track marshal, Horner gave a stark warning to his rivals."Vettel is continuing to get stronger, continuing to get better," Horner said. "He is a very focused and determined young man, and has achieved a huge amount in his career. But the impressive thing about him is how much desire he has to continue to improve. He obviously wants to achieve as much as he can."SEBASTIAN SACRIFICEVettel on Sunday (June 9, 2013) claimed his third win this year and the 29th of his career as well as his first for Red Bull in Canada, opening up a 36-point lead in the Drivers' championship.Horner said there was evidence, too, that Vettel may be willing to sacrifice some of his youthful exuberance, like chasing the fastest lap in the closing stages, for overall success."Some things don't surprise us, like the fastest lap thing - which of course he was going for. I said to Rocky (Vettel's race engineer), 'Get him under control'. So, he said to Sebastian after he went purple on the first sector: 'Monaco 1988, Senna'.”In that race, Ayrton Senna, in pole, posted the fastest lap and was leading by 50seconds until he spun and crashed out, handing victory to his rival Alain Prost."I thought that might work and Sebastian came back on the radio and said, 'Alright, I am only joking' - with a purple sector. So he backed off."EYE ON ALONSODespite Vettel's lead in the title race, Horner also saw no reason to believe that his team was now in the driving seat for the championship."While the points look healthy at the moment, Fernando Alonso put in another strong race and you cannot afford for any complacency. The margins can rapidly be eroded."Two-time champion Spaniard Alonso of Ferrari finished second in the race ahead of battling Lewis Hamilton of Mercedes.After the race, it was announced that a marshal had died following an accident at the Circuit. The marshal was helping to retrieve Mexican Esteban Gutierrez's crashed Sauber car following the race when he tripped while trying to retrieve a dropped radio and fell under the wheels of a mobile crane. He is third marshal to have been killed at Formula 1 grands prix since 2000. Stay with Wheels24 for the 2013 F1 season – fresh reports every day.