"I had expected it to be tough and it was," Nishikori said.
"I'm not confident yet so I can't hit aggressive shots. It's going to take some time. I made mistakes where I shouldn't have, and there are a lot of gaps I need to fill. There were both good and bad."
Nishikori was ninth in the world rankings before suffering the injury ahead of the Cincinnati Masters last August.
He had been hoping to make his return at the season-opening Brisbane International, where he was runner-up in 2017, but withdrew from that event to continue his recovery.
The 28-year-old became the first Japanese man to reach a grand slam final at the 2014 U.S. Open but did not compete at Flushing Meadows last year because of his injury.
Counting the positives, Nishikori said he did not feel any pain during his one hour, 47-minute match.
"Just because I didn't play well today, I'm not going to get negative. I'll keep working hard," he said.
(Reporting by Sudipto Ganguly in Mumbai; Editing by John O'Brien)
Share
