On 2 February 2008, Khan was scheduled to fight Martin Kristjansen, but illness forced the Dane to withdraw and instead Khan beat Australian Gary St Clair in a contest for the Commonwealth lightweight title at the ExCel Arena in London. This was his first fight to last all 12 rounds and was won via a unanimous scoring from all three ringside judges.
On 5 April 2008, Khan beat Kristjansen in the seventh round of a WBO world lightweight title eliminator. Before the contest, the fighters had been ranked third and fourth respectively by the WBO. After Khan’s victory, he was ranked second, behind only Joel Casamayor.
Following the fight, Khan split from his trainer Oliver Harrison, the trainer for all of his previous 17 professional contests. The breakup was blamed on Harrison’s concerns that Khan’s public engagements were interfering with his fight preparations. Khan’s spokesman told reporters there was “nothing personal” between Khan and Harrison. Dean Powell, who has trained former world champions Duke McKenzie and Lloyd Honeyghan, worked with Khan until a decision on a permanent trainer was made. In the same month, Khan had a training session in Las Vegas with Roger Mayweather, trainer and uncle of Floyd Mayweather, Jr
Khan fought on 21 June 2008, at the National Indoor Arena in Birmingham against Irishman Michael Gomez. Gomez, a super featherweight champion who was reaching the end of his career and had lost the last one of his six fights, was described as a “backward step” in Khan’s quest for a world title. Khan stated “I think I’m above this level now” and made it clear that he expected a fast and explosive finish to the fight knocking down Gomez two times in the fight and a great finish. However, after the fight, Khan said he felt he had moved up a level by “fighting a good fighters like Gomez”. Khan received criticism for being knocked down in the second round, but proved his resilience by coming back stronger after this. Former boxing champion Barry McGuigan seemed unimpressed after the fight and said Khan needed at least two more fights before he should consider a world title bout. Many journalists[who echoed McGuigan’s opinion of Khan’s needs to work on his defence.
A month after the Gomez fight, it was announced that Jorge Rubio would become Khan’s new trainer. Rubio was chosen because Khan thought that he had very good chemistry with the Cuban trainer. Khan said, “Rubio was showing me all these new training techniques, and I felt so comfortable because it suited my style. I knew I had the hand speed and the footwork to do it and I knew it was going to make me a much better fighter”. Many boxing experts thought that Rubio needed to concentrate on improving Khan’s defence and Khan’s father agreed that he was showing great defensive skills during his training.
In early August, the lightweight Breidis Prescott was chosen by Rubio as Khan’s next opponent. Rubio had trained a fighter who had narrowly lost to Prescott before and thought that Khan would be able to handle the bigger Prescott, who had a prolific knock-out record of 17 KOs in 19 contests. On 6 September 2008, Khan was a huge favourite and was hoping to win a world title by the end of the year. Prescott came out fast in the fight and landed some good shots; Khan was stumbled with a left hook early on before Prescott landed a strong overhand right, flooring his opponent. He managed to get to his feet but following a further four punch barrage, Khan was knocked out and couldn’t beat the count. It was officially over in 54 seconds. The fight was at the Manchester Evening News Arena on Khans Sky Box Office debut.
Following his defeat to Prescott, Frank Warren sacked Khan’s trainer Jorge Rubio and replaced him with Freddie Roach. Khan began training with Roach in the United States, where he sparred with then WBC World lightweight champion and p4p champion Manny Pacquiao, who is also being trained by Roach. On 6 December 2008, Khan recorded a comeback win against Oisin Fagan in a second-round stoppage. With victory, Khan won the vacant WBA International lightweight title. Khan knocked Fagan down twice in the first round and Fagan’s corner threw in the towel in the second, after being knocked down again.