If Stanislas Wawrinka has really been as “insecure” and lacking in self-belief as his coach (Magnus Norman) was suggesting as recently as last September, I hate to see what’s going to happen when he decides that he is, indeed, worthy.

Wawrinka gave as good as he got on the court in 2013, and the better the opposition, the more enthusiastically he blasted his big, booming one-handed backhands and slippery, relatively flat forehands. Make a short list of the best matches of 2013 and Wawrinka features in something like three of the top half-dozen.

It all came to a head at the U.S. Open, where Wawrinka pummeled No. 6 Tomas Berdych and defending champ Andy Murray to reach his first Grand Slam semifinal. He faced off with Djokovic and once again came up just a bit short—just like at the Australian Open, in a punishing five-setter highlighted by superb shotmaking by both men.

That outstanding run helped Wawrinka qualify for the season-ending World Tour Finals, where survived the round-robin but lost in the semifinals to Djokovic. It was a fine capstone to what is, thus far, Wawrinka’s career year (51-23, with a title at Oeirias). Is there more to come in 2014?

Ad-In: If Wawrinka’s well-documented struggle with self-doubt is indeed a thing of the past, he’ll do a lot of damage with his punishing serve and heavy groundstrokes. This guy is as strong as an ox but surprisingly quick around the court. He could easily surpass rivals in the bottom half of the Top 10 and pose a constant threat to the very top men.

Ad-Out: When a guy has struggled as long as Wawrinka has with confidence, it’s hard to imagine that the enemy has been banished for good. If he rests on the laurels he earned in 2013 and takes a few bad losses, the old ghosts could return to haunt him.

As we approach the new year, we'll take a closer look at what's in store for the past year's top performers. To read more of our 2014 Season Previews, click here.