The Spaniard, who saved two match points in a testing opening match against Lucas Pouille, was imperious under pressure as he fended off all six break points he faced.
He will face John Isner in the last eight after the American sixth seed thrashed Leonardo Mayer 6-0 6-3.

China Open men's results

Tennis
Federer 'really inspired' by Nadal, hopes to 'hit ground running' on return
2 HOURS AGO
Second round
1-Rafa Nadal (Spain) beat Karen Khachanov (Russia) 6-3 6-3
6-John Isner (US) beat Leonardo Mayer (Argentina) 6-0 6-3
Roland-Garros
French Open: Who has the best draw? Who are the dark horses?
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Roland-Garros
Raducanu, Swiatek to face qualifiers, Osaka gets tough opening clash
21 HOURS AGO