Johanna Konta was ejected from the US Open in what is the biggest upset of the tournament so far.
The seventh seed was knocked out in the first round by the unseeded Serbian Aleksandra Krunic, 4-6 6-3 6-4.
Konta, 26, spoke about her disappointment to BBC Radio 5 Live: "It's definitely not an easy defeat to take - it was a close match. It went to three sets and over two hours. I try to keep a very good perspective on how this sport works and that is there are no easy matches.
"First rounds are always tricky and difficult, regardless of the tournament but I guess especially in Slams, so I think that's for everybody, not just me.
"My opponent dealt with it and I competed until the very last ball, so I can't be too harsh on myself in that sense, but I've definitely got a lot to improve on, which is also a positive thing."
The Briton had been hoping to improve on previous semi-final appearances at Wimbledon and the Australian Open.