Second-ranked American Steve Johnson, currently ranked No. 37, is aiming higher up the rankings in 2015. Johnson defeated Marinko Matosevic in the first round of Brisbane before falling to world No. 5 Kei Nishikori, 6-4, 7-5.

The top-ranked American is No. 18 John Isner, a former college player at the University of Georgia. Very few four-year college players have become top players, but Isner and Johnson, who went undefeated during his time at the University of Southern California, are notable exceptions.

"Definitely the ranking goals are there," Johnson told "I really want to come down here and do well and kind of impose myself, and not prove that last year was kind of a fluke or I did it on accident over the course of a few months. I know I'm a good tennis player, and I want to come down here and start off the year and show guys I'm not an easy out. I've improved a lot over the last six months, and I want to show guys that. I want to go out there and use my competitiveness."

Johnson hired a new coach in November, the Dutch native Peter Lucassen, who used to work at USC.

"One of the things I'm most of proud of about myself, I don't give up or throw in the towel," Johnson added. "I really like to go out there and compete. If a guy is too good that day, he's just too good. But I'm going to make him earn it.”