Berlin, June 13 -- Seventeen-year-old Justin Engel reached the Stuttgart Open quarter-finals to become the youngest player since Boris Becker, 40 years ago, to reach the last eight of an ATP Tour grass-court tournament.

The German wildcard beat American seventh seed Alex Michelsen 6-4 6-4 on Thursday to continue a stunning week for the teenager

Engel had earlier became the second youngest player since 1990 to win an ATP Tour match on all three surfaces - grass, clay and hard court - after Rafael Nadal.

He now follows in the footsteps of compatriot Becker, who reached the quarter-finals at Wimbledon as a 17-year-old in 1985. Becker went on to win the title that year.

Engel will next play Felix Auger-Aliassime for a place in the semi-f...