By Gary Smith, World-Track
Johnson, the current 400m world record holder who held the previous 200m world mbest, before losing it to Bolt last year, says even a fast finisher like Gay would have a difficult time in fending off the towering Jamaican if he gets out with the field.
"Gay understands that his only chance of beating Bolt is to take the lead early and exploit Bolt’s only weak spot, which is his start," Johnson said.
"Unfortunately for Gay, the start of the 100m is only the first 10 per cent of the race and so that is Gay’s small window of opportunity.
"He then has to hold that lead for the remaining 90 per cent against an athlete who, I have been told, is capable of covering the 100m in 41 steps compared to mid-forties for the average sprinter."
Gay will start the championships as the defending sprint double champion, after over taking Asafa Powell to win the 100m and blasting away from Bolt to take the 200m two-years-ago in Osaka.
But Johnson reminded that things would be more difficult for his fellow American, as Bolt had already grown out of being a potential world beater and has immerged into the world superstar he now is.
"Gay is the defending world champion at 100 and 200 metres, but due to injury last year did not compete in the 200m and did not make it past the semi-final in the 100m. This is his chance to defend his titles and regain the top spot," Johnson said.
"But when Gay was last on top in 2007 and on his way to realising the potential he showed when he first came on the scene, his biggest rival was Asafa Powell, then the world record holder, but an athlete who most sprinters know cannot handle the pressure of major championships.
"Bolt was just a young Jamaican sprinter with a tremendous amount of talent at 200m. Things have changed dramatically and Gay was in the race in New York last year when Bolt turned into the fastest man in the world when he beat the field to set a world record for the 100 metres at 9.69sec.
"Bolt went on to win the 100 and 200m in amazing fashion in Beijing, and Gay and all sprinters had to completely rethink what is possible and what it will take to win championships."