Singapore, Tianjin in China and Monterrey, Mexico are now battling to win the right to stage the prestigious season-ending event which each year features the top eight singles players of the season. Monterrey has replaced Mexico City as Mexico’s bidding city. Kazan in Russia had been on the initial shortlist announced in October but the WTA has now ruled out taking the tournament there. WTA chairman and chief executive Stacey Allaster will now visit the three cities, starting in Monterrey this week. She will head to Singapore next month and Tianjin in March. A final decision on the venue will be made in April. The event is this year due to be held in Istanbul – the third and final year of the Turkish city’s deal. Serena Williams won the title there last season.