Ramanathan, ranked 248th, won his only previous match on tour at this event two years ago. On Thursday, he defeated Alexander Kudryavtsev of Russia, a lucky loser who replaced injured second seed Kevin Anderson, 3-6, 6-4, 6-4. Ramanathan became the first Indian to reach the Chennai quarters in two years.
Fabbiano came into the week with an 0-6 career record on the tour and managed to double his win count in upsetting Muller, a quarterfinalist last year.
Paire, last year's ATP comeback player of the year for climbing from out of the top 100 to No. 19, put away Lukas Rosol of the Czech Republic 7-5, 7-5, and Aljaz Bedene of Britain, the runner-up last year, took more than two hours to defeat Luca Vanni of Italy 5-7, 6-3, 6-4.