Moscow (AFP) - Kremlin Cup top seed Svetlana Kuznetsova and Carla Suarez Navarro expressed caution on Tuesday over their prospects of securing a ticket to the end of term WTA Finals in Singapore.

Both are in with a shout at grabbing a late pass due to the defection of Serena Williams.

If either wins in Moscow they will edge out Johanna Konta of Britain - who was forced to bypass the Kremlin Cup with an abdominal injury - for the eighth and final qualifying singles spot for Singapore.

US superstar Williams announced on Monday she was pulling out of the elite WTA Finals as she was still working to recover from the shoulder troubles that hindered her this year.

Kuznetsova said her main objective was to play her best tennis in front of her home crowd.

"If I manage to get a pass to Singapore, that would be great," she said. "But the situation is so uncertain and now I'm much more anxious about my performance here."

Suarez Navarro said: "I need to go step by step, from match to match because there are plenty of strong players and every match here in Moscow will be tough for sure.

"If I manage to go all the way here I'll make it (into the WTA Finals) but there is still a long way to the final and especially to the title."

The tournament in Singapore will see Agnieszka Radwanska defend her title against current top seed and world No. 1 Angelique Kerber.