The big-serving American has come to life indoors, scoring his second Top 10 win in the last two months to reach the final four at the Swiss Indoors Basel.
The No. 20-ranked 20-year-old extended his winning streak against Top 20 players to five matches in a row on Friday with a 7-6 (5), 6-3 victory over No. 11-ranked Stefanos Tsitsipas in Basel.