Kristina Mladenovic ramped up the pressure on Maria Sharapova ahead of their Suttgart semi-final when she claimed the Russian superstar was getting "extra help" in her comeback from a 15-month doping ban.

Sharapova eased into the last four of the clay court tournament by seeing off qualifier Anett Kontaveit for the third straight win of her comeback.

The 30-year-old five-time Grand Slam winner has yet to drop a set and powered past Estonia's Kontaveit, ranked 73rd, for a 6-3, 6-4 quarter-final win.

The Russian former world number one has been given wild cards by tournament organisers in Stuttgart, Madrid and Rome and played her first match back here on Wednesday, much to the irritation of many of her rivals, including Frenchwoman Mladenovic.

"In sport nowadays it is also about the media and business. Maria is a big name, who makes people come to watch her," said world number 19 Mladenovic after her 6-3, 6-2 win over Spain's Carla Suarez Navarro.

"On one hand, I totally understand the tournaments want her in the draw, because she is very famous and they want more attention, which is part of the business.

"On the other hand, you can ask if it is fair to get a wild card. It's a fact that she was caught by anti-doping, but she wasn't the first one.

"Others have also had the right to come back and play tennis, but with a different road, they wouldn't get invitations to tournaments.

"Of course, she is authorised to play tennis again, but why would she get that extra help compared to other players?"

Sharapova gave a terse answer when asked if Mladenovic's comments would motivate her in Saturday's showdown: "Not at all".

"I am not someone that uses it as part of my comeback," she said after beating Kontaveit.

"I have let my tennis do the talking. My results have spoken for everything that needs to be said. The biggest part of my comeback is what happens on court."

Some bookmakers already make Sharapova the favourite for next month's French Open, even though she is not currently guaranteed a place due to her lack of a ranking after her ban.

However, if she wins Sunday's final, Sharapova will rank approximately 125th in the world — high enough for a qualifying place at both the French Open and Wimbledon.

Sharapova was again impressive against plucky Kontaveit, firing down four aces, 28 winners and hitting just two double faults. She also converted five of her six break points.

Mladenovic said she has been impressed with Sharapova's form in beating Roberta Vinci and Ekaterina Makarova in previous rounds in Stuttgart.

"She has been quite impressive, she has not played for a long time and has come back, beating players with different styles," said the 23-year-old who lost her only previous match against Sharapova, in straight sets in the Wimbledon first round in 2013.

"I think she is still mastering her 'A Game'. I didn't see anything new, I think she is just playing her game really well, like she did in the past."

Sharapova has won three Stuttgart finals, suffering just one defeat, in her four previous appearances.

Her path to the final was eased when second-seed Czech Karolina Pliskova lost 7-6 (7/3), 5-7, 6-3 to Germany's Laura Siegemund in an epic 3hr 10min duel.

By contrast, Romanian fourth seed Simona Halep needed just 59 minutes to down Latvia's Anastasija Sevastova 6-3, 6- 1.