Rising American star Ben Shelton fought back to reach his first ATP Tour final at the Japan Open on Saturday after a semifinal win over qualifier Marcos Giron.

The 21-year-old beat American world number 79 Giron 6-7 (2/7), 7-6 (7/5), 6-4 in Tokyo to set up a showdown with either Russia's Aslan Karatsev or Japanese wild card Shintaro Mochizuki.

Shelton was appearing in the second semifinal of his young career after reaching the same stage at the US Open last month.

He threw away a winning position to lose the first set but battled back from two breaks down in the second to tie up the match.

Shelton then rode the momentum to take the third set, closing out the match with an ace before letting out a roar and thumping his chest.

World number 19 Shelton is the highest-ranked player left in the tournament after a week of upsets.

World number 215 Mochizuki knocked out American top seed Taylor Fritz in the second round.

Germany's Alexander Zverev and Norway's Casper Ruud also exited the tournament early.

RESULTS:

Ben Shelton (USA) bt Marcos Giron (USA) 6-7 (2/7), 7-6 (7/5), 6-4