Sharapova's 15-month drugs ban for testing positive for meldonium officially ends at midnight tonight and she is due to play her first competitive match since the 2016 Australian Open against Vinci at the Porsche Arena.

The return of the five-time Grand Slam champion has dominated the build-up to the Women's Tennis Association (WTA) Tour event in the German city and her presence is likely to be the focal point during the tournament.

Organisers of the event enabled her to play her first round match tomorrow - the exact day her ban ends.

Sharapova will not even be allowed to enter the Porsche Arena until then.

The 30-year-old, a three-time winner of the competition, was given a wildcard back in January - a decision which has been met with opposition from players on the Tour.

Former world number one Caroline Wozniacki of Denmark hit out at Porsche Grand Prix officials in March and Vinci, currently ranked at 35, has become the latest to question the decision.

"I don't agree about the wildcard here and about the wildcard in Rome and the other tournaments," said Vinci. 

"I don’t have anything against her. 

"She made her mistakes for sure, but she paid and I think she can return to play, but without any wildcards, any help.

"Probably she would play two or three tournaments and be in the top 30 for sure. 

"Probably there are a lot of players who are agreeing with me about the wildcard."

In announcing Sharapova's wildcard, tournament director Markus Günthardt claimed it was "justified" due to her "successes in tennis and her popularity for the tournament".

The 30-year-old could be given similar treatment at next month's French Open at Roland Garros in Paris, with the French Tennis Federation due to make a decision on whether to grant her automatic entry on May 15.

Sharapova was initially banned for two years by the International Tennis Federation (ITF) before her suspension was reduced to 15 months by the Court of Arbitration for Sport (CAS) in October.

CAS ruled that her case was "not about an athlete who cheated" and that she was not an "intentional doper".

Main draw action in Stuttgart got underway today, with Anastasija Sevastova of Latvia overcoming Australia's Sam Stosur in three sets, 6-1, 4-6, 6-3.

Barbora Strýcová of the Czech Republic eased into round two as she comfortably beat American Jennifer Brady 6-2, 6-2.

She was joined by Anett Kontaveit of Estonia as she dispatched Croatian Ana Konjuh 7-5, 6-4.