"I got off to a slow start and he served well in the first set," said the world No 8 Chang, who is ranked 235 places above the ATP Tour newcomer, Radulescu. "I started to play better after that and he missed a few serves. A combination of those things helped me back into the match."
Chang will now meet Kenneth Carlsen, of Denmark, whom he beat in three sets in the second round at last week's Japan Open. The Dane reached the last eight of the event with a 6-4, 2-6, 7-6 victory over the seventh seed Jan Siemerink, of the Netherlands.
"I had a tough match against Carlsen in Tokyo and I am sure he is eager to play me again - it will be difficult match," Chang said.
The former world No 1 Jim Courier, who beat the current No 1 Andre Agassi to win in Tokyo last week, had a sluggish opening set before hitting form to defeat his fellow American Jonathan Stark 7-5, 6-1 in their second- round match. "It was a bit blustery out there and both of us were distracted by the wind," the third-seeded Courier said. "I improved as the game went on and I'm happy about that."
Sweden's Jan Apell recovered to reach the last eight with a 6-7, 6-3, 6-3 win over the eighth-seeded Martin Damm, of the Czech Republic.
In Nice, Andrei Medvedev shrugged off recent injury worries to crush the Spaniard Javier Sanchez and reach the quarter-finals of the Nice Open. The fourth-seeded Ukrainian never looked in trouble on his way to a comfortable 6-0, 6-3 win.
"After a few physical problems, I feel fine again and I enjoy playing tennis," said Medvedev, looking forward to next month's French Open. "Hopefully, I will be able to do well there and to give the best players in the world a hard time."
Medvedev now meets the Australian Richard Fromberg, who beat the Spaniard Alex Corretja 6-4, 6-2 in a second-round match.
The fifth seed, Marc Rosset of Switzerland, also reached the last eight by beating Spain's Roberto Carretero 6-4, 6-3. The hard-hitting Rosset will face the Australian Mark Woodforde for a place in the semi-finals.
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