Jenson Brooksby has confidence he can compete with anybody after threatening a fourth-round upset against Novak Djokovic at the US Open.

The unheralded American posed a real problem for Djokovic at Arthur Ashe Stadium and took out the opening set 6-1 in New York City.

It was not to be, though, as Djokovic – chasing a calendar Grand Slam – roared back to win 1-6 6-3 6-2 6-2.

Despite falling short, Brooksby is only looking at the positives from going toe-to-toe with the world number one in such a huge match.

"It's definitely all positive things to take away. I learned my game. I'm feeling really confident in my game. I believe I can compete with anybody," Brooksby said after his first run to the second week of a grand slam.

"I knew it would be important to start strong, to impose my mindset and my strategy, my game out there. It's definitely special. I mean, I always enjoy the matches and everything throughout the moment. Obviously you have to stay focused.

"Afterwards, you can always have time to reflect more. Just appreciate and enjoy for the whole journey.

"Atmospheres like that are what you want to be in front of since you were a little kid, watching on TV when you were young, and now you're living it. It is something I really appreciate and I'm grateful to be here now. I'm excited to keep [playing] in atmospheres like this for the future."

Brooksby required treatment a couple of times during the match and revealed he was contending with an issue to his left hip.

"Yeah, there was something. Something that kind of came up from later in the second match, then in the third one. Even with a day off, then kind of into today, like my left hip kind of was bothering me even early on and more into it," he added.

"Not like it's an excuse or anything, but it kind of went throughout the leg today a bit. I was struggling more to push off and move. But that's part of the sport. I did everything I could to feel the best I can going out there today and all the other days. There's no regrets on that.

"I definitely think if there wasn't that, I could have kept a better level up closer to the first set throughout the rest of the match."

Brooksby only reached the world's top 100 earlier this month and is now projected to be on the cusp of the top 40.

The 20-year-old relished his first experience of playing on Arthur Ashe.

"I did take time to look around a little bit, just appreciated being in an atmosphere like that with so many people cheering you on. Took a moment to still have it all in after," he said. 

"You're not going to win every match you play obviously, but you still have to enjoy it.

"I think [the belief] comes from definitely more training, but most importantly other match situations against other guys and just the whole process of it. 

"Leading up to it, I 100 per cent believed I could win against anybody. I thought I showed that with the level I could produce out there. Unfortunately, physically it got a little tougher."