Petkovic, Goerges set up all-German semi
Andrea Petkovic advanced to the semi-finals at the WTA Citi Open, with Ekaterina Makarova, Oceane Dodin and Julia Georges claiming wins in Washington.
Finally appearing to overcome extensive injury problems, Petkovic's 6-7 6-1 6-2 win over Bianca Andreescu secured her first WTA semi-final appearance of 2017.
The 17-year-old Canadian wildcard made it difficult, but the world number 102 didn't help matters with nine double faults.
Petkovic's victory sets up a match against compatriot, Julia Goerges, following her 6-3 6-4 win over Monica Niculescu.
The German fourth seed served 12 aces on her way to victory, also winning 49 per cent of points on return of serve.
After top seed Simona Halep retired hurt to put Makarova through, French fifth seed Dodin saw off Sabine Lisicki in three sets, winning 5-7 6-4 7-6.
Neither showed any confidence on serve, with Dodin and Lisicki putting up 14 and 11 double faults respectively.
Dodin eventually held her nerve, taking out the closing tie-break 7-4.