Stanislas Wawrinka came into this week’s ATP World Tour Finals as a dark horse to win. With names such as Rafael Nadal, Novak Djokovic and Roger Federer in the field, it is easy to overlook the Swiss star. But overlook him at your peril, especially after he defeated Tomas Berdych in three sets on Monday to open round-robin play in London. That victory came in Wawrinka’s first appearance at the prestigious season-ending event. Regardless of his result there, he has put together a season to remember in 2013.

To the casual fan, Wawrinka flies under the radar compared to more familiar names, but his consistency has been impeccable. He has not ranked outside the top 30 since March 2008. For years, however, he had lived in the shadow of the legendary Swiss superstar, Roger Federer. That began to change this season for the 28-year-old. 

Wawrinka did not start the year in a position that would lead many to reason that he would qualify for the World Tour Finals. However, during the course of his 2013 campaign, he left a trail of top-10 victims in his wake, ranging from Andy Murray and David Ferrer to Tomas Berdych, Jo-Wilfred Tsonga and Richard Gasquet. (In fact, he defeated Murray and Berdych on both hard courts and clay.) Wawrinka also reached the second Masters 1000 final of his career in Madrid, where he upset Tsonga and Berdych. With that outstanding 2013 record against the elite, he clearly earned his way into the World Tour Finals.

Two notable events may have defined Wawrinka’s resurgence this season. One took place early in the year in Melbourne. There, Novak Djokovic faced the Swiss No. 2 in the fourth round at the Australian Open. In what turned out to be an epic battle, it took five hours and two minutes for then-world No.1 Djokovic to advance, taking the fifth set 12-10. Wawrinka had come within five points of victory earlier in the set and had rallied boldly to force that set by winning a fourth-set tiebreak. No other man would come nearly as close to derailing Djokovic en route to his latest Australian Open title. Despite the painful loss, Wawrinka earned respect for his resilience.

At the US Open in September, Wawrinka posted his best result at a major by advancing to the semifinals, defeating Berdych and Murray along the way. Ultimately, it was Djokovic who stopped him once again. This time, it took four hours and nine minutes before the Serb advanced in another five-setter. And, once again, Wawrinka earned a new legion of fans with his tremendous effort in New York.

As remarkable as it sounds, Wawrinka may have overtaken his friend and compatriot, Federer, with whom he won an Olympics gold medal in doubles five years ago. Coming into the World Tour Finals, each Swiss man has just one title under his belt this year. But Wawrinka gained nine ranking spots this season, while Federer fell five. About 500 points separate the two players, but the younger Swiss star has recorded eight victories over top-10 opponents this year to his compatriot’s two. Thus, Wawrinka may finally be stepping out of the legendary Federer's footprint.

At 28 years of age, Wawrinka still appears to be in his prime and has made strides in establishing himself at majors. His first-round Wimbledon loss can be viewed as an aberration based on his recent success against a number of elite competitors. When the calendar turns to 2014, his performance at tournaments such as the Australian Open is something to keep in mind when searching for a dark horse who can challenge the elite when it matters most.