Second seed Grigor Dimitrov slumped to a 7-6 (4) 6-3 loss to world number 155 Jerzy Janowicz at the Stuttgart Open on Thursday.
Janowicz made the most of the momentary lapses in concentration by Dimitrov to book an unexpected quarter-final spot.
Earlier, number three seed Tomas Berdych beat Australian Bernard Tomic 7-6 (4) 6-2 to qualify for the last eight.
The Czech professional tennis player will face Feliciano Lopez in the quarter-final after the Spaniard beat France’s Jeremy Chardy 6-3 3-6 6-2.
