Michael Johnson is the king of the quarter-mile so it pays to listen to him when he turns his attention to Christine Ohuruogu, Britain's solitary Olympic track champion. “Who is the best female 400 metres runner in the world?” he asked himself. “Hands down, it's Sanya Richards.”

If Ohuruogu needed any additional motivation as she prepares for her first showdown of the season with the American at the Bislett Games in Oslo this evening, Johnson's assessment provides it. “I like Christine,” the 400 metres world record-holder and four-time Olympic champion said. “I just think that at some point she's got to come out. It's not going to continue to happen for her when she goes to the championships and the best 400-metre runners in the world don't run to their capabilities.”

That is the curious conundrum for both women. Richards has run under 50 seconds on 34 occasions, while Ohuruogu has managed it twice. However, those times netted her gold medals at the World Championships in Osaka, Japan, in 2007 and the Beijing Olympic Games last year. It is an imbalance that puzzles Johnson. “Sanya Richards is notorious for not running to her capabilities,” he said. “She can't get it done at championships, but that's not going to continue. For Christine's sake she needs to get out there and run faster. She can't rely on running a 49-second 400 metres. She's relying on people not getting it done.

“If you look at it realistically, has she outperformed the best athletes in the world? No. They didn't perform. I'd want to control my destiny and think, 'I'm not concerned by what they run because I know I'm going to go fast.' All she's doing is preparing to run at a level and hoping they don't run faster.”

Ohuruogu has been concentrating on the 200 metres this season to sharpen up her speed, leaving the stage free for Richards to post world leading times. However, Johnson's appraisal does not take into account matters such as race craft and the view that Ohuruogu drags every vestige of ability from her body when it matters. She has said that she believes that she can dip below 49 seconds, but that would constitute a significant improvement.

Richards has admitted that the pressure gets to her. She has even spoken of basing herself away from the United States team at the World Championships in Berlin next month so that she can live in a vacuum and ignore the hype. “She doesn't have that type of killer instinct,” Johnson said. “There are some athletes who are very good at that, but when the pressure is on you have to run a different type of race.”

He is glad that Ohuruogu is taking on Richards this evening. “I think there is more to come from Christine, but the only way she's going to improve is to go out there and run against these people, not just stay home, train and turn up at the championships. That's not the way she is going to get to the level which I think she can get to.”

There are other duels to savour in Oslo, albeit Tirunesh Dibaba, of Ethiopia, has pulled out of her 5,000 metres battle with Meseret Defar, a compatriot, but from a British perspective the single-lap showndown is the most intriguing. However, the clever money is on Ohuruogu failing to light up the stadium in the way Andy Baddeley managed in winning the Dream Mile a year ago because she has said that her only focus are those three races in Berlin.

She has also tried to play down her rivalry with Richards, but the latter has varied her tune over the past two seasons. In 2007 she backed Ohuruogu's bid to overturn her British Olympic Association ban for missing drug tests, but she previewed their clash in Beijing by saying that she was lucky to be there. If Ohuruogu beats Richards this evening, she will deny her the chance of scooping the $1million (about £610,000) Golden League jackpot, which comes from winning your event at all six meetings. If that is not enough of a motivation, Johnson's words might just be.