- London Olympics 2012
Holmes backs Greene to complete the set
The world 400m hurdles champion, also has gold medals from the 2010 European and Commonwealth Games, with Olympic gold the only title to elude him.
Greene finished second to Javier Culson at the London Grand Prix last week, but has returned to form following surgery at the end of 2011.
And Holmes, who won 800m and 1500m gold at the 2004 Athens Games, is confident the Welshman can peak at the right time and grab gold in London.
"I really believe that he can [win gold] and it would be again an amazing achievement," Holmes said. "If he can get the gold at the Olympics he then has the full lot of Commonwealth, European, world and Olympics and the only other person to do that was Sally Gunnell in the 400m hurdles."
Mo Farah cemented his status as a medal contender with victory in the 5000m at Crystal Palace, although the 10,000m will be his top priority. Kenya and Ethiopia have dominated long-distance running in recent years, but Holmes believes Farah, who moved to Britain from Somalia when he was eight, can claim a historic victory on home soil.
"How amazing would it be to have an Olympic champion at one of the distance events for the first time in a long time and the first time ever, I think, in the 10,000 so that would be great," she added.