Ukrainian teenager Dayana Yastremska advanced to the quarter-finals of the Adelaide International after former world No 1 Angelique Kerber retired with an injury while losing 6-3 2-0.

The 19-year-old started extremely impressively as she took the first set with 11 winners and just four unforced errors as Kerber looked to be struggling to keep pace.

And the same pattern of play continued at the start of the second set as the three-time Grand Slam champion was broken in the opening game as her confidence appeared to be diminishing.

Having lost the first two points of the third game, Kerber then decided to retire from the match as Yastremska booked her place in the last eight.

She will face Croatia's Donna Vekic for a semi-final spot in Adelaide after the current world number 19 beat Maria Sakkari 2-6 7-5 6-1.

After failing to get out of the blocks and losing the first four games of the match, Vekic grew into the encounter as she forced Sakkari to a decider.

And Vekic closed out the match with a run of eight games from the last nine to seal her place in the last four against Yastremska.