Fourth seed Myneni, who has become the second-highest ranked Indian in singles at 168, pipped Spain's unseeded Gerard Granollers 6-4 7-6(3) in the first round of the USD 50,000 ATP Hard Court Challenger event.
Nagal and Jeevan Nedunchezhiyan however bowed out after suffering first round defeats while Sanam Singh's match suspended due to rain.
Myneni had raced to a 4-1 lead in the second set but the Spaniard won four of the next five games to make it 5-5 and stretched the issue to a tie-breaker.
"It was a tough match as the conditions were not easy. It's been raining now and then, so it is very humid. It was one of those matches that one needed to play smarter. Gerard started playing better and forced me to go a bit extra with my shots. I am glad that I played a good tie-breaker to seal the match," Myneni told PTI.
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Upcoming talent Nagal, who won the junior Wimbledon doubles title in July this year, showed that he was making good strides on the professional circuit.
After being bagled by the Spaniard in opening set, Nagal made a superb comeback to take the second set. The match changed in the fourth game of the third set when the Spaniard broke Nagal.
The Indian was spanking the ball hard but Menendez-Maceiras retrieved amazingly from both the flanks and found a winner to go up 30-0. Nagal hit an inside-out forehand just outside the lines and was facing three breakpoint now.
The Spaniard took a long medical time out but returned and finished the job quite smoothly. Nagal had quite flashy ground-strokes and if he could have kept them inside the lines, the fight would have been tighter.
Left-hander Nedunchezhiyan, who qualified for the main draw, lost tamely 2-6 2-6 to Japan's Hiroyasu Ehara.
Sanam after losing the first set 1-6, was leading the second 5-1 against Germain Gigounon when rain stopped play.