Former World number one tennis player Jim Courier gives his take on why Americans no longer dominate the men's game.
Americans in the past have dominated men's singles with the likes of Pete Sampras, Andre Agassi, Andy Roddick and Courier, amongst others, all previously ranked as the world number one..
But for the last few years there has been no American players near the likes of Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray, who have totally dominated the sport in recent times.
In a chat with the Tennis World website, Courier gave his thoughts on where he felt the problem was.
"Well because we are in the era of the big four. I don't think anyone has been able to break through there. It has been very difficult, when you have Federer and Nadal and now Djokovic dominating" Courier said.
"And, Murray right behind, chasing those guys. I don't really care what flag you play for.
"Those are four incredible tennis players playing at the same time. It has been tough for everyone. I know our guys are trying hard, they are doing everything that they can but it's really a unique era.
"I think in a few years we will look back at this time with more admiration of what these guys are achieving and currently have which is hard to fathom.
"It's pretty remarkable, how much they are admired right now. In three to five years, the era of the big four will be past us.
“There will some opportunities then for guys to win majors and get up to number one."