Click here to find out more! Sport > Athletics Idowu's late withdrawal fuels injury concerns for Olympics

The clouds were gathering in Birmingham even before the best of Britain's runners, jumpers and throwers got about the business of chasing Olympic places on the opening day of the Aviva 2012 Trials last night. There was another of a metaphorical nature when it emerged that Phillips Idowu had withdrawn from the three-day meeting.

The 2009 world triple jump champion has not competed since landing awkwardly during the Eugene Diamond League meeting on 2 June and news that he would be absent from his event this afternoon inevitably fuelled suspicion that he might be suffering from a not-insignificant injury a month out from the London Olympics. "It is not a worry," Charles van Commenee, the UK Athletics head coach, maintained. "Phillips is a strong medal contender."

Still, Idowu's condition remains a mystery, Van Commenee declining to say whether the 33-year-old Belgrave Harrier was injured. "There is an area of medical confidentiality," he said. "This is all I have to say."

Van Commenee, of course, had a public falling out with Idowu on the subject of his tweeting last summer. As of last night, though, Idowu had posted nothing relating to his fitness or state of health on the social networking site.

There were no problems for the major home Olympic hopefuls in action last night. Dai Greene (400m hurdles), Christine Ohuruogu (400m) and Mo Farah (1,500m) were all comfortable heat winners. "It was a good bit of speed work," Farah said.

The speediest bit of work came in the first race of the night, the opening heat of the men's 100m. Adam Gemili underlined his status as the man to beat in the blue riband event. The 18-year-old former Dagenham & Redbridge academy team right-back heads the British rankings this summer with 10.08sec and he impressed when he clocked the fastest winning time, 10.27sec, despite easing down in the final 10m.

The chances are that there will be a changing of the British sprinting guard when it comes to the final today. Dwain Chambers has been beaten just once in the national championship final since returning from his drugs ban, but knows he will need to move up a gear to beat the burgeoning Gemili.

Chambers won the 60m bronze medal at the World Indoor Championships in Istanbul in March but has only clocked 10.28sec for 100m this summer, 0.10sec shy of the Olympic "A" standard qualifying time he needs if he is to take advantage of the outlawing of the British Olympic Association byelaw that precluded former drug offenders from Team GB selection. "It's going to be tough with the young boy there," Chambers said. "The seniors need a kick up our butts to get going."

Kenenisa Bekele needed something similar when it came to the final race of the night. Despite being the reigning Olympic champion at 10,000m, the Ethiopian required a quick time as one of the East African guests to book his place in his country's team for London 2012. He did in style, sprinting to victory in 27min 02.59sec, the fastest time by an Ethiopian this year and a UK all-comers' record.