The WTA Insider Heat Index is your guide to the hottest performers on the WTA tour. It's not about ranking points or Slam wins, it's about the moment. The Heat Index is about the here and now: who's hot and who's not, going into the most important swings of the season. The goal is to give WTA fans and commentators a snapshot of who are the hot hands on tour.

The Heat Index takes the following factors into consideration: performance over recent weeks, quality of wins, general form, historical performance, past success at upcoming tournaments, injuries and coaching changes, as well as the ever so subjective "gut feeling".

Five weeks into the 2018 WTA season, here are the ten hottest players heading into the hard court events at the Qatar Total Open (Premier 5) and Dubai Duty Free Tennis Championships (Premier). 

1. Caroline Wozniacki (Current Ranking: No.1)
2018 record: 12-2
Recent Results: Australian Open champion, Auckland finalist, WTA Finals Champion, Tokyo Champion
Key Stat: The 2018 Australian Open champion has made the final or better in three of her last four events (WTA Finals - Won; Auckland - Final; Australian Open - Won; St. Petersburg - Quarterfinal).

2. Simona Halep (Current Ranking: No.2)
2018 record: 11-1
Recent Results: Australian Open finalist, Shenzhen champion
Key Stat: Halep has either won or made the final of the two tournaments she's played in 2018. Her sole loss of the year came to Wozniacki. 

3. Angelique Kerber (Current Ranking: No.9)
2018 record: 10-1
Recent Results: Australian Open semifinalist, Sydney champion
Key Stat: Kerber began her season at Hopman Cup where she went undefeated in singles, notching wins over Eugenie Bouchard, Elise Mertens, Daria Gavrilova, and Belinda Bencic. Including those matches in her win-loss record would move her to 14-1 on the season so far, an outstanding clip given her 2017 struggles. 

4. Elina Svitolina (Current Ranking: No.3)
2018 record: 9-1
Recent Results: Brisbane champion, Australian Open quarterfinals
Key Stat: En route to her 10th career title in Brisbane, Svitolina earned two Top 10 wins over Karolina Pliskova and Johanna Konta. An injury hampered her performance in Melbourne, where she lost to Elise Mertens, but Svitolina enjoyed a breakout week in Dubai last year, where she won her first Premier 5 title. 

5. Julia Goerges (Current Ranking: No.10)
2018 record: 9-2
Recent Results: Auckland champion, WTA Elite Trophy champion, St. Petersburg semifinals
Key Stat: The German's 15-match win-streak finally came to an end in the second round of the Australian Open but she rebounded well to make the St. Petersburg semifinals, losing in a high-quality three-set match to eventual champion Petra Kvitova. That run launched her into the Top 10 for the first time. 

6. Elise Mertens (Current Ranking: No.20)
2018 record: 9-1
Recent Results: Australian Open semifinalist, Hobart champion
Key Stat: The 22-year-old Belgian kicked off her season by defending her title in Hobart and did not lose a set en route to her first Slam semifinal, where she lost to eventual champion Wozniacki. 

7. Karolina Pliskova (Current Ranking: No.5)
2018 record: 6-2
Recent Results: Brisbane semifinalist, Australian Open quarterfinalist
Key Stat: The defending champion in Doha, Pliskova has now made the quarterfinals or better at five of her last six Slam appearances. Her two losses this year came to Top 5 players, losing to Svitolina in Brisbane and Halep in Melbourne. 

8. Petra Kvitova (Current Ranking: No.21)
2018 record: 6-2
Recent Results: St. Petersburg champion
Key Stat: Kvitova rebounded from a heart-breaking 6-3, 4-6, 10-8 loss to Andrea Petkovic in the first round of the Australian Open to knock off three Top 15 players en route to her 21st title in St. Petersburg, beating Jelena Ostapenko, Julia Goerges, and Kristina Mladenovic in dominant fashion.   

9. Ashleigh Barty (Current rank: No.16)
2018 record: 6-3
Recent Results: Wuhan finalist, Zhuhai semifinalist, Sydney finalist, Australian Open third round
Key Stat: The youngest player on this iteration of the Heat Index, Barty has continued to build on her strong finish to the 2017 season, which saw her make the biggest final of her career in Wuhan by defeating Agnieszka Radwanska, Johanna Konta, Karolina Pliskova, and Jelena Ostapenko before falling in three sets to Caroline Garcia. After making her third Premier final in Sydney last month, Barty had made two Premier finals in her last five events. 

10. Caroline Garcia (Current Ranking: No.7)
2018 record: 3-3
Recent Results: Australian Open quarterfinalist
Key Stat: Garcia suffered a back injury in her first event of the year in Brisbane but came back strong to make her first Australian Open Round of 16.