Two of Britain's brightest athletes erred on the side of caution yesterday as Dean Macey announced he would not be competing at this year's World Championships and Katharine Merry, who helped Britain's 400m relay team to second place in last weekend's European Cup, pulled out of Sunday's scheduled return to individual 400m racing after a two-year gap.

Macey, who has been troubled by a series of problems including the hamstring injury which kept him out of competition last summer, has been advised by his medical team that he is not fit enough to try and add another world medal this year to the silver he won in Seville four years ago and the bronze he took in Edmonton in 2001.

The 25-year-old Canvey Islander was scheduled to compete at the Spar European Cup of Combined Events in Tallinn, Estonia, on 6 July, where his intention was to achieve the World Championship qualifying standard - a plan Britain's Olympic champion Denise Lewis is also pursuing there.

But Macey, who was fourth in the 2000 Sydney Games, now intends bidding for the Olympic qualifying mark at the Decastar meeting in Talence at the end of September. "I am content with the change of plan," he said. "It enables me to fully return to my maximum capacity instead of rushing my fitness and risking the injury and poor performance at the European Cup.

"Obviously I am sad to be missing out on the World Championships, as I will not have qualified. However, I see the Olympics as my ultimate goal and that mean I have to make sacrifices along the way."

The same philosophy has prompted Merry's decision not to risk running in the Norwich Union International at Glasgow's Scotstoun stadium this weekend, just a week after making her return to international action in Florence despite having a foot ligament problem which required two injections.

Speaking from her Cardiff training base, the Olympic bronze medallist said: "I am frustrated that I have to make decisions about my season's racing programme on a race-by-race basis.

"However, my focus must still be to get through this season without aggravating any old injuries or picking up any additional problems. My current plan does not go beyond competing in an individual 400m at the Norwich Union Super Grand Prix in Gateshead on 13 July."