MANCHESTER (AFP) - Amir Khan hopes his 19th professional fight and first with new trainer Jorge Rubio will offer a strong argument for his defence on Saturday. Being deposited on the canvas for the third time in his professional career in his last fight against Michael Gomez has prompted the unbeaten English lightweight to hire a new trainer. That scare also convinced Frank Warren, the British promoter, that Khan is not ready yet to challenge the likes of Nate Campbell, the American who defends three versions of the world lightweight title against Joan Gunman, of the Dominican Republic, in Mississippi on September 13. So, instead, Khan is seeking to extend his unblemished record against Breeds Presto, of Colombia, with the World Boxing Organisation (WBO) Intercontinental lightweight title on the line at the MEN Arena in Manchester.   After sag Oliver Harrison earlier this year, Khan used another British trainer, Dean Powell, in his last fight in June during which the 2004 Olympic silver medallist's defensive frailties were again exposed.   Gomez, a former British super-featherweight champion who is past his prime, managed to floor Khan, who had previously been knocked down by Scotland's Willie Limond and France's Arched Drilzane.   Khan regained his composure to hammer out a fifth round stoppage win over Gomez, but the second round knockdown was enough to convince him to employ an additional trainer to Powell for the Presto fight.   Khan, 21, has experienced new training methods under Cuban Rubio, who is a former coach of the formidable Cuban amateur team and is nonbiased in America.  Khan, whose lightening fast fists have stopped 14 opponents confidant his work with Rubio will show a tighter defence against 25-year-old Presto, who has assembled an unbeaten 19-fight record with 17 stoppages.Been working on defensive moves and keeping my hands up and it has been a completely new thing working with Jorge," Khan told AFP. He has taught me to keep my hands up more and made my defence tighter, so you'll see an improvement in my defence on the night. "I've been doing a lot of different things in training and have adjusted really quickly and smoothly to working with Jorge. " It wasn't ideal getting knocked down by Gomez, but it taught me a lesson and I'm glad it happened. "I am going to use my brain, work off the jab, work in and out and work the speed. I'm going to put in some big power shots to slow him down a bit and then put the pressure on him. I've worked on keeping my hands up more, but I still love being a showman and giving the crowd value for money. It's going to be another step up for me to take me closer to where I want to be, fighting for a world title," he said. Also on the bill, Alex Arthur will make the second defence of his WBO world super-featherweight title against fellow Briton Nicky Cook. Arthur, 30, produced an unspectacular performance when he out-pointed England's Stephen Foster Junior in December. But the Scotsman claims he has made the weight easier this time for Cook, from London. "I had to lose eight pounds in the week before the Foster fight which wasn't ideal but this week it has only been two pounds which is a massive difference," Arthur told AFP.