LONDON: Russian prodigy Mirra Andreeva, playing in her first senior grasscourt tournament at the age of 16, upset her compatriot and 22nd seed Anastasia Potapova 6-2 7-5 on Sunday to reach the fourth round at Wimbledon.

Andreeva, who had to come through qualifying, was playing her sixth match of the tournament but looked fresh and composed on Court Three and produced some stunning strokes to down her seasoned 22-year-old opponent.

The teenager, ranked 102 in the world, caught the eye when she reached the third round at her first Grand Slam at the French Open last month and has now gone one better.

She took the first set on Sunday in half an hour before Potapova had time to settle, with a rare move to the net and a volley winner.

Potapova found some range and consistency at the start of the second set and broke twice to lead 4-1 but Andreeva discovered new reserves of energy and fight and took three games in a row.

A clearly frustrated Potapova then needed to defend seven break points in an exhausting game lasting almost 10 minutes.

But Andreeva was undeterred and continued to show remarkable maturity and calm. She broke serve for 6-5 and triumphed after an hour and 35 minutes when Potapova dumped a lob into the net.

Andreeva will play American Madison Keys, the 25th seed, in the fourth round.