#2 Caroline Wozniacki
The Dane became World No.1 in 2010 and held the position for a total of 67 weeks. She had a phase of decline in 2012 and 2013 but snapped out of it soon and made her second Grand Slam final at the 2014 US Open which helped her return back to the Top 10 and later to the Top 5.
However, in 2015, she had a string of disappointing results which propelled her to fall out of the Top 10. Wozniacki had a decent start to her year by reaching the semi-finals of the ASB Classic before putting on a career-worst performance at the Australian Open where she bit the dust in the opening round to Yulia Putintseva.
Injuries led to her withdrawal from Roland Garros and as a result, her rankings dropped from 22 to 34. After a disappointing start to the grass court season, Wozniacki was beaten in the first round of Wimbledon by Svetlana Kuznetsova and as a result, she fell out of the top 50 for the first time since 2008.
After disappointing showings at the Citi Open and the Rio Olympics, Wozniacki then played at the US Open. After surviving a scare in the first round against Taylor Townsend, Wozniacki avenged her Wimbledon defeat by beating Kuznetsova in straight sets.
She continued her good form and produced another upset of the competition by beating eighth-seeded Madison Keys in the fourth round to reach the quarter-finals where she beat Latvian Anastasija Sevastova to reach her first Grand Slam semi-final in nearly two years.
She lost to eventual champion Angelique Kerber but the semi-final finish was enough to put her back in the top 30 at 28th. With a stellar and clock turning performance at the US Open, we can surely expect a lot from Wozniacki in the forthcoming tournaments.