With the gap between the American No. 1 and the next level widening, many American men have converged on the Houston clay courts hoping to not only prepare for Roland Garros but better position themselves behind John Isner.

Isner has spiked to a ranking of world No. 9, a position he last held in April 2012. The North Carolina native has accomplished this behind a title in Auckland and two semifinal appearances, most recently at the Indian Wells Masters 1000. He finds himself in a comfortable environment, entering the U. S. Clay Court Championships as the defending champion. By repeating his success there, Isner could close the gap on world No. 8 Andy Murray. After retiring in the first round of the Australian Open, he finally appears healthy. Barring additional injuries, a spot in the year-end ATP World Tour Finals in London is a reasonable goal.

Although Isner has produced encouraging results this year, Sam Querrey has encountered adversity. The man who had solidly positioned himself behind Isner as American No. 2 has plummeted down the rankings. Querrey has endured a difficult start to 2014, advancing past the second round in just one tournament. Additionally, he was involved in a disappointing Davis Cup loss for the United States, where he saw a lead slip away against Andy Murray after a collapse against James Ward. As a result, Querrey has yielded the honor of American No. 2 to Bradley Klahn, while he has dropped to world No. 82.

While Querrey has struggled, Klahn racked up early points this year via back-to back Challenger titles that fueled his climb to world No. 65. However, when using his Challenger success to compete in ATP events, Klahn struggled in those tournaments. He fell in the first round of Delray Beach, Indian Wells and Miami. Klahn was forced to pull out of the Houston tournament this week, a tournament he described as “definitely one of my favorite events on the calendar!”

Perhaps the hottest American man beyond Isner is Steve Johnson, who enters Houston on the heels of a Guadeloupe Challenger title last week. Johnson made a semifinal run at Delray Beach after an Irving Challenger title earlier in the season. With these successes, he has moved within four ranking spots of the absent Klahn and could become the American No. 2 with success at the U. S. Clay Court Championships. A wildcard in Houston, Johnson has shown success at larger venues and will be dangerous on American soil. He has already notched victories against Tommy Haas and Feliciano Lopez in the United States this year.

Americans Jack Sock (above) and Donald Young are in the Houston draw as well as they cling just inside the top 100. But both have lacked the consistency to make a serious run towards the top 50, seemingly taking one step forward and two backwards. Still, along with Klahn and Johnson, they make up two of four Americans in the top 100 who are under the age of 24 and are still young enough to progress.

Interestingly, with the shuffle of American players behind Isner, the top three consist of players who competed four years in college. Georgia, Stanford and USC are represented by these three. With questions consistently surfacing as to the state of American tennis, has college become the most successful route for players from the United States?

Former college stars Klahn and Johnson both relatively young, so there is plenty of time and potential to follow in Isner's footsteps towards the top. Since Houston is the last ATP tournament in the United States until July, all of the top American men will look to make a large imprint there before heading to clay and grass in Europe in the coming months.