Cadel Evans's immediate race future is in doubt with the 2011 Tour de France champion suffering from a suspected "low grade infection".
Evans will travel to Milan, Italy this week to undergo tests. He was forced to withdraw from the recent USA Pro Cycling Challenge during the sixth stage due to a knee problem.
"Despite his usual full commitment and attention to training Cadel has been experiencing unusual up and downs on his performance," BMC team doctor Max Testa said in a statement. "Getting him back to full health and to his physiological standard of performance is a priority for the BMC Racing team."
Testa added Evans could return to racing at the Grand Prix Cycliste de Montréal, in Canada, on September 9 - dependant on test results.
The 35-year-old has had a mixed season. He won the Criterium International in March, finished third at the Criterium du Dauphine in June and was seventh overall at the Tour de France. Evans appeared unwell during the final week of the Tour and was forced to withdraw from the Olympic Games time trial, after competing in the road race, citing fatigue.
"I didn't know what was holding me down at the time," Evans said. "Now we have a better idea, and it's a relief to have some indicators as to why I have been under-performing. When you don't know why you're not performing, you have to ask a lot of questions of yourself.
"It's been disappointing for me, but I'd like to thank my team-mates and people who are close to me - my family and so on - for supporting me during this frustrating period. The first thing is to get healthy and then come back to my best."
Evans's teammate Thor Hushovd has also been suffering from an infection that has derailed much of his season.
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