If the WTA gave out an award for unpredictability, it would be neck and neck—as well and shank and shank—between Sabine Lisicki and Petra Kvitova. You never know what’s going to come off of their strings next; the only safe bet is that it won’t be what you expected.

The injury-prone Lisicki has always had the ball-striking chops to win a Grand Slam. In 2013, at age 24, she finally showed them to the world by upsetting Serena Williams on her way to reaching the Wimbledon final. The fact that Serena herself wasn’t especially surprised by her defeat should tell you all you need to know about Lisicki’s talent. Unfortunately, the German's freeze-up in the final on Centre Court a few days later was all you need to know about her reliability.

Grass remains Lisicki’s best surface, and the All England Club is the one place where she puts everything together. But that success has yet to carry over anywhere else. After Wimbledon, she reached just one semifinal the rest of the season.

Ad-In: Lisicki has putaway power, which is a prerequisite for Grand Slam success. Now that she knows she can go all the way, or almost all the way, at a major, the confidence should be there to do it again. Should. In reality, she’ll probably have to wait until her beloved Wimbledon to show us what she can do.

Ad-Out: More of the same. Lisicki has too much game to sink too far in the rankings, and not make an occasional deep run at an event. But with her power, anything less than a Top 10 finish feels like a disappointment.

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.