Chela, who won his fourth career title in Acapulco earlier in the year, is 19th in the ATP Rankings, just four places below his career-high mark.
Swiss Stanislas Wawrinka, who had just three ATP match wins this year before this week, reached his first quarter-final of the season with a 6-4, 6-1 win over Croatian qualifier Marin Cilic.
Czech qualifier Jiri Vanek rallied from a heavy first-set loss to defeat Gael Monfils 1-6, 7-6(4) 6-2, avenging his loss to the Frenchman in Gstaad last week.
Vanek reached his first quarter-final of the year and faces Wawrinka in the third round.
Mirza through to quarter-finals
Third-seeded Sania Mirza of India became the first quarter-finalist at the Western and Southern Financial Group Women's Open on Wednesday with a 6-2, 6-2 victory over Varvara Lepchenko of Uzbekistan.
"When I set up my schedule this year, I wanted to skip Cincinnati, but my dad [Imran] said, `You always play well in Cincinnati,'" Mirza said. "I like the heat. It feels a lot like India when I play here."
Mirza will make her third quarter-finals appearance in three visits to the tournament. She lost last year to this year's second seed and the 2005 champion, Patty Schnyder, and to seventh-seeded Akiko Morigami in 2005.
Top-seeded Anna Chakvetadze of Russia also moved into the quarter-finals with a 6-4, 6-3 victory over qualifier Anda Perianu of Romania in the only evening singles match. The eighth-ranked Chakvetadze, who fell behind 0-4 before winning 12 straight games in her opener on Tuesday, trailed 3-1 on Wednesday before regaining form.
No. 2 seed Mueller advances
Second-seeded Martina Mueller advanced to the quarter-finals of the Palermo International on Wednesday with a comfortable 6-2, 6-1 win over Conchita Martinez Granados.
It's only the second time this year that the 34th-ranked German has won consecutive matches.
Italian wild card Sara Errani also reached the quarter-finals, beating Eva Birnerova of the Czech Republic 6-2, 6-0.
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