Zheng Saisai never considered herself the defending champion of the Zhengzhou Open despite her triumph last year.

World No 38 Zheng defeated compatriot Wang Yafan in last year's final when the tournament was still a 125K series event on the WTA calendar.

It has since been upgraded to Premier 700 level, with a $1.5 million prize pool attracting a number of top-10 players and former Grand Slam champions to give the tournament a glitzier feel.

With a tougher field to negotiate, Zheng is not comfortable with calling herself the reigning champ.

"You cannot call me the defending champion of the Zhengzhou Open because the level of the tournament is very different from last year," Zheng said after defeating world No 155 Bibiane Schoofs of the Netherlands (7-6, 6-1) on Tuesday to set up a second-round meeting with American world No 34 Alison Riske on Thursday.

"This year, the Zhengzhou Open is a brand new tournament. For me, I'm familiar with this city, I've played many matches here and I know the whole atmosphere. This time there are more spectators and fans to support me.

"The tournament's upgrade is also a good news for local tennis lovers as they now have a better chance to see the world's best play in their hometown."

Zheng won her first WTA title at last month's Silicon Valley Classic in California and was a women's doubles finalist at this year's French Open. She also reached the US Open doubles quarterfinals with Duan Yingying last month and is partnering with her compatriot again in Zhengzhou. She said switching back and forth between the two disciplines is not easy.

"Because I spent a lot of time playing doubles, I'm still trying to find my pace in singles," she said.

"It's been a while since I last played singles, so I'm adjusting. The next round and the possible match after that will be much harder."