Konta’s brilliant run to the semi-finals of Wimbledon marked her out as a contender for the title in New York on her favoured hard courts and she went into the tournament as one of eight players in the race to be world number one.
But the 26-year-old never looked comfortable against 78th-ranked Krunic and lost 4-6 6-3 6-4.
Konta said: “She played very well. She played consistently much better than I did. I think she was able to raise her level throughout the match, and mine fluctuated a little bit up and down.
“So I think in terms of effort and fight, I competed until the very last point. I think the level of tennis by her was just better today.
“First rounds in every tournament, and especially at slams, it can be tricky, finding your footing and playing yourself into the tournament, into the match.
“She played quite freely, and I think she was able to find her level much quicker and more consistently. That’s credit to her for dealing with the situation better than I did.
“It’s definitely not an easy loss to take. I would have liked to have been involved here for much longer.”
This was Konta’s second first-round loss of the season at a grand slam after she was beaten by Hsieh Su-wei at the French Open.
But the 26-year-old struggles on clay and had never won a match at Roland Garros while she had made the fourth round on her last two visits to Flushing Meadows.
She said: “My only responsibility is towards me and towards the work I do and make sure I do myself justice, and also the team around me who work very hard alongside me.
“I have no full control over the outcome of any match. I have control over the things that I bring to the match, so I felt I really competed as best as I could.
“I don’t take anything for granted. I had an incredible Wimbledon experience, but I have moved on since then.”
Konta insisted she felt happy with her preparation despite only winning two matches in the build-up to the tournament having taken a short break after Wimbledon.
Krunic looked a good draw on paper but the Serbian showed how dangerous she can be here three years ago when she defeated Madison Keys and Petra Kvitova on her way to the fourth round.
She will now head home to Eastbourne to spend some time with her parents before resuming her season in Asia next month.
Konta said: “I think not to catastrophise it is important. At the end of the day, it is a tennis match. I think to have a healthy perspective on that,