Thomas was selected for but later withdrew from the Great Britain road race team citing fatigue at the end of a season that included the spring classics, Tour de France, in which he assisted Chris Froome (Sky) to overall victory, and the Vuelta a Espana.
British Cycling technical director Shane Sutton today said Yates would substitute Thomas in the September 27 road race, and that there was "no replacement for Cav at present".
The 2011 world champion Cavendish, according to reports, will today (Friday) make a decision as to whether to start the 259.2km road race in North America.
The 30-year-old crashed out of the Tour of Britain last week where he injured his shoulder.
Yates made his first senior appearance with Team GB at the world titles in Spain last year.
The 23-year-old has performed since his Tour de France debut with trade outfit Orica-GreenEdge in July and should bolster the nine-man squad that will assemble for the open circuit race in Richmond, Virginia, which includes cobbles and punchy climbs.
Watch: Yates vs Yates
Yates bettered Philippe Gilbert (BMC) to win Clasica San Sebastián in his first race back from the Tour in August. Earlier this month he finished second overall at the Tour of Alberta, behind Bauke Mollema (Trek), and was runner-up at the one-day GP de Montreal, behind Tim Wellens (Lotto Soudal) on Sunday.
It's not clear what role Yates will play in the race.
His brother, Simon, following the announcement of the original squad that included Thomas, told CyclingNews he was not surprised the Girona-based duo were not selected.
“I don’t think that it’s a course for myself or Adam to do well in, maybe on the day and in certain conditions, but I haven’t seen the course, only heard what people have said. We had a quick discussion and there are better riders to help the leaders," he said.
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