The 23-year-old Devvarman, who is based in the U.S., produced an inspired display to triumph in 2 hours and 14 minutes in hot conditions in the southern Indian city to move into his second ATP tour quarterfinals.
Sixth seed Moya won the first set comfortably but Devvarman, who spent his formative years in Chennai, delighted the home crowd when he grabbed the second set.
The highest-ranked Indian at 202, Devvarman broke the Spaniard in the third game of the final set as he wore down the former world no. 1 for the biggest victory of his career.
Moya said he was at a disadvantage with organizers scheduling matches in the heat of the Chennai afternoon to make up for matches that had been delayed by rain.
"The heat affected me more than it bothered him,'' Moya said.Devvarman became the first Indian player to reach the quarterfinals in Chennai since Leander Paes reached the semifinals in 1998
"(Devvarman) plays much better than his rankings reflect,'' Moya added.
"I was not surprised, because I saw him play two days ago and knew he was very fast and was solid from the back of court.''
"I sent a message to him that I just wasn't going to go away," said Devvarman.
"When you see a player on the other side trying to do too much, you know he's under pressure."
"Hopefully, I'm not just quarters. I'm not one of those guys who gets content easily,'' he added.
(Via supersport.co.za, sportsillustrated.cnn.com)