Maria Sharapova's comeback from a doping ban went from strength to strength on Friday, the Russian advancing to the semi-finals of the Stuttgart Open thanks to a hard-fought victory over Anett Kontaveit. 

The 30-year-old has excelled in her first tournament back following a 15-month ban for failing a drugs test at the 2016 Australian Open, and she kept that momentum up with a 6-3 6-4 win at the WTA Premier event.

She will now face Kristina Mladenovic or Carla Suarez Navarro for a place in the final, as the prospect of securing the title after receiving a controversial wildcard entry appears increasingly likely. 

Kontaveit initially held her own against the power game of the Russian, the first set remaining on serve through the first six games.

The turning point arrived when Sharapova broke with a fierce cross-court backhand, forcing Kontaveit to net her return attempt.

That proved the trigger for the former world number one to pull clear, holding rapidly by dispatching a short, lobbed return from out wide into empty space on the other side of the unguarded court.

Kontaveit was clearly shaken, offering up three set points on her own serve, Sharapova taking the second of them courtesy of an inch-perfect backhand winner down the line.

The Estonian recovered her composure to fight hard early in the second set, but struggled to compete when the five-time grand slam champion stepped things up, breaking in the fourth game by combining a perfectly weighted drop shot with some crushing winners from the baseline. 

Kontaveit showed spirit to break straight back, a backhand winner kissing the baseline to offer hope, but it was quickly dashed by the irresistible force on the other side of the net, Sharapova breaking again by forcing a forehand error after a demanding rally. 

Sharapova's first two double faults of the match while serving to win it delayed the inevitable in what proved to be the longest game, Kontaveit eventually taking a fifth break point to extend the contest.

Another marathon game followed but this time it was Sharapova who dug deepest, a backhand winner settling a thrilling rally to bring up advantage, before a Kontaveit error finally handed her passage into the last four.