Newly demoted world number two Ash Barty is on the trail to regain her number one ranking but the first obstacle she'll have to overcome is one of the modern era's most phenomenal and divisive players - Maria Sharapova.

Barty will face the four-time Grand Slam champion - one of few left on the WTA circuit to have won all four majors - in the Round of 32 of the Cincinatti Masters after Sharapova disposed of Barty's newest rival, Allison Riske.

The American was the downfall of Barty at Wimbledon, the key factor in the Aussie 23-year-old losing her number one crown, so there is a personal vendetta at stake when these two meet on Thursday.

The two have faced twice, with 81st ranked Sharapova (the result of injuries and a doping-related suspension) holding a 1-1 record.

But while Barty is suffering a slight dip after her French Open victory, Sharapova is far from the height of her powers, failing to make it past the second round in her last three tournaments.