Grigor Dimitrov refused to be too hard on himself following a US Open semi-final defeat to Daniil Medvedev he felt was decided by the Russian's performance on a few key points.

Dimitrov sensationally knocked out Roger Federer in five sets in the quarter-finals to set up a clash with Medvedev, having come from two sets to one down to defeat the 20-time grand slam champion.

However, Dimitrov was not able to make the necessary breakthroughs when it mattered against world number Medvedev, who claimed a 7-6 (7-5) 6-4 6-3 victory to progress to his first major final.

Dimitrov, though, felt the match was closer than the three-set scoreline suggested, with the Bulgarian left upbeat by a run few expected when he started the tournament ranked 78th in the world.

"It was just a few points here and there. Yeah, three sets to love, but, I mean, the score for me doesn't justify the match itself," Dimitrov told a media conference.

"I think it was a good level. Overall he played really well, fought hard, a lot of the key points he played well. I don't want to be too down on myself. Great weeks. First time in the semi-final out here.

"Just going to take a lot of the positives, for sure."

Dimitrov identified the set point he spurned in the first set by clanging a forehand into the net cord and wide as a key moment in the contest.

"As I said, I just didn't play good enough on those key points, especially I think the set point in the first set, I knew what he was going to do. He came up with the goods," added Dimitrov.

"Second set, again, I was not able to get free points on my serve, or on his for that matter. He used the court pretty well.

"For sure I'm critical of myself. I think absolutely I could have done better on certain occasions. Again, I don't want to go too deep right now on myself.

"I will definitely watch the match and see if I could have done any different in any type of situations. But I think, again, a few times it was 30-All, 30-15, [he] just came up with the goods. I came up to the net, it was either a pass or a really good ball, bottom line.

"So I had to go for something very difficult. In a sense, he was provoking me to miss certain shots that I usually wouldn't miss or I would have enough time to hit a volley. Just the small details.

"I do believe I've given everything of myself out there in the match today. I still felt that I could have done something else, I just don't know what it is right now."