TOKYO, Japan (AFP) — Rising tennis star Ben Shelton said Friday that his career had moved "a lot faster than I would have thought" after advancing to the semi-finals of the Japan Open.

The 21-year-old has quickly made a name for himself since turning professional in August last year, reaching the quarter-finals of the Australian Open in January and the semi-finals of the US Open last month.

The world No. 19 beat fellow American Tommy Paul 7-6 (7/4), 6-3 in Tokyo to move a step closer to his first ATP Tour title, and said he was "really happy with the way things are going."

"I didn't think right away that I was going to be a pro as soon as my college career was over, that I would be on the main ATP Tour this quickly," said Shelton, who will play another American, Marcos Giron, in the semi-finals.

"Definitely things have moved a lot faster than I would have thought when I was in college."

Shelton said he is still taking classes at the University of Florida but would have to "see if it's something that I continue to do" or decide to leave his education until later.

He gave the Tokyo crowd another glimpse of his undoubted talent with an impressive win over Paul, the fifth seed who he also beat at the US Open.

Shelton said he had to play "more within myself" to deal with the strong wind blowing around the stadium.

He was happy to continue his recent run of form after reaching the quarter-finals of last week's Shanghai Masters.

"Wins are tough out here on tour so to get three in a row is something that's a pretty cool feat for me, something that hasn't come often for me yet in my career so far," he said.

"The last three tournaments I've played, I got at least three wins so definitely really excited about the way things are going for me."

Shelton has also become known for celebrating wins with his now-trademark "dialled-in" gesture with an imaginary telephone.