Petra Kvitova's progression to the last four of the WTA Finals was confirmed as fellow Czech Lucie Safarova beat Angelique Kerber in straight sets on Friday.

Having lost control of her own fate courtesy of a defeat to Garbine Muguruza earlier in the day, Kvitova was given a reprieve when Safarova - whose hopes of securing a last-four place had already been dashed - eliminated Kerber with a 6-4 6-3 triumph.

Kerber required just a set to qualify from the White Group alongside Muguruza, but was well beaten by an opponent who served well throughout.

Kvitova will therefore face Maria Sharapova in the last four, while Muguruza faces a match against Agnieszka Radwanska.

Asked if she had provided Fed Cup team-mate Kvitova with the perfect gift in an on-court interview, Safarova laughed before replying: "Teamwork! I'm happy for her that she won through to the semis and happy for my win as well."

Kvitova duly tweeted: "Omg. Thanks @luciesafarova."

The day's earlier match featured 15 breaks of serve and there were three in succession at the beginning of this contest.

Safarova claimed the initial advantage, the Czech's forehand working well as she enjoyed success in each of Kerber's opening two service games.

Two set points went begging for Safarova in game nine, but it mattered little as she held comfortably to move ahead.

The loss of the first set prompted Kerber to adopt a more attacking approach, which brought immediate rewards in the form of a hold to love.

However, Kerber was then broken again as she followed a double-fault with a weak forehand into the net and with Safarova maintaining a high first-serve percentage, there was to be no way back for the sixth seed.

Kerber saved three match points when serving to keep the match alive at 5-3 down, but then went wide to give Safarova a first win in her final outing of the week.