"It was good (the win against Wang Yihan) but in my book she can do a notch higher. There's of course some chances of improvement in a couple of areas," Gopichand said after Sindhu earned a hard-fought 22-20 21-19 win over world number two Wang to make the semis.
Sindhu gave away six easy points at a crucial stage in the second game to hand Yihan a 19-18 lead, but the Indian did well to scrape through in a 55-minute battle of nerves.
"She's been inconsistent a few times and squandered leads but I think it's part of her learning experience. She's still young, and has age on her side. I think she's a great fighter with great work ethic," Gopichand said about the 21-year-old Indian.
Rating the win as one of the biggest of Sindhu's career, her coach said, "I think definitely, it's one of the biggest. The (Olympic quarterfinal) stage makes it special. She played really well and was all fired up."
"It was really a good match, a spirited performance from the beginning. Both the players fought well. Sindhu stayed calmer and finished off. She showed great attitude.
"Sindhu straightway got into a a good retrieving capacity to negate Yan's attack. It was very close call on all the games.
"She changed her gameplan a couple of times and started attacking on Sindhu's forehand then she played counter net a couple of times. In the end, Sindhu backed up well with some solid smashes," he said.