All sports and all countries have regularly seen times when they have struggled to produce world-class players. The exact reasons haven’t been discovered but a period of high in a sport for a country has more than often than not been followed by a dry spell.

Take the examples of the Australian cricket team immediately after the Bradman era, or the mighty West Indies in the 90s after being dominant until the late 80s - even Indian hockey in the latter part of the 20th century. Times of bright sunshine have always been succeeded by dark nights.

When it comes to tennis, we need to understand the situation in its entirety. Previously, while most countries produced one or maybe two world-class players at a time, the US would produce about a dozen. And when you have such a number, you have more chance that somebody from your side will take the centre stage.

Now that the sport has become big the world over, countries which hardly figured on the world tennis map are producing players left, right and centre. It is nothing more than a coincidence that US men’s tennis is having a slight lull at the same time. James Blake and Andy Roddick are phenomenal players but they haven’t been good enough.

The reason for worry may not remain for long as the American tennis factory is busy processing some future world-class players. The competition in US tennis has become very tight in the last couple of years and some young boys have made their way up the rankings at an astonishing pace. If the alarm bells are still not ringing at other tennis federations they might be in for a drubbing.

Standing at 6ft 6in tall, Sam Querrey was born in San Francisco in October 1987. He managed to qualify for US Open before turning 19 and the following year he qualified for the other three Grand Slams as well and making it to the third round of the Australian Open in both 2007 and 2008. He has a huge serve, a crafty forehand and hits powerful shots off a two-handed backhand.

He regularly won titles in his junior days and has performed brilliantly on the ITF circuit. He turned down a scholarship offer from the University of South California to turn pro. He is referred to as “the new Todd Martin” because of his height and the Davis Cup Captain Patrick McEnroe has already touted him as the nation's “next great talent”.

In 2007 a boy called Donald Young won the Boys Singles title at Wimbledon and created huge waves when he entered the third round of the men’s singles at the US Open - his very first time in the men’s category at a Grand Slam tournament. Born in July 1989, at the age of ten Donald got the opportunity to play with John McEnroe when he was a ball boy at the US Open.

McEnroe could read it then and there and said about Young: “He has hands like another lefty I know very well.” He turned pro in 2004 and, from a ranking of 1,253, climbed to 575 in 2005. He broke into the top 100 in 2007 and is currently ranked 88. The speed of his ascent warrants caution for others.