The new Grandstand stadium at the Billie Jean King National Tennis Center, home of the U.S. Open, was again the scene of an emotional American story Wednesday, as underdog Ryan Harrison defeated Milos Raonic in a three-hour display of grit and talent.

After the sensational match between John Isner and Frances Tiafoe on opening day – an apt baptism for the new structure which is already a fan favorite, packed solid for every match — it was fitting that on the first day of second round competition a young phenom should making a clear statement that American men’s tennis is on the way back to the glory days of yore.

And it is particularly fitting that the statement should be made by Harrison who, though only 24, already has had his share of peaks and valleys. Hailed as an heir of Agassi and Sampras when only a teenager, the Shreveport native with the elegant form and unshakeable grace under pressure has been through some difficult patches due to injuries and the inevitable realities of an extremely competitive tour.

Indeed his opponent, the big serving Canadian No. 1 (born in Montenegro), who is a year older than Harrison and is ranked No 6 in the world to the American’s 120, has experienced some of the same difficulties, and has faced them like a pro, with work, not whining. The match on Wednesday was nothing if not a clash of gentlemen.

Raonic played a more dominant game. He had more winners, more aces, and was like a stone wall at the net, which he approached often, both on serve and on defense. But Harrison held on against the barrage of aces and volleys and got the passing shots and the corner winners when they were needed. He lost the first set and was down 1-3 and 2-4 in the third, but did not lose his cool.

It was, indeed, the remarkable control over four sets, rather than the fact of beating a high-seed, high-rank opponent, that made this the most important match Harrison has played in a long time, if not ever. Several games in the second and third sets went to deuce and got stuck there for four or five or more points; all of these nail biters were on Harrison’s serve. He held. Or he held enough of them.

He was aided in the fourth set by the disintegration of Raonic’s game, beginning in the middle of the third set. Cramping in the left thigh, for which he called a trainer, visibly affected his service and his movement. Overall he doubled 15 times and often seemed like a ballplayer of whom you say “strikes out looking.” The pain clearly frustrated and slowed him.

But frustration and pain in tennis do not come out of nowhere. The pressure of Harrison’s bullets to the corners, his deft and unreachable passes, were the decisive factor over the three and a half hours of play. He had trouble with his serve too (12 doubles), but he did not let it infect his ground game; Raonic’s powerful forehand sailed increasingly wild as the match progressed and his backhand, notably on the return of serve, kept finding the net.

With Tuesday’s win by 19-year old Jared Donaldson (rank: 122) over Belgium’s David Goffin (rank: 14) , who was seeded 12^th, John Isner’s defeat of another Belgian, Steve Darcis, in second round play on Wednesday, and first round wins by Donald Young and Steve Johnson, there is reason to expect Americans to be in contention into the second week.  If not, there remains the consolation that the bench is getting deeper and more confident.

It is gratifying that Ryan Harrison is finding his place in the new, or renewed wave, of the post-Sampras-Agassi cohort, who maybe were written off too soon. The teens coming up behind them are competitive threats and colleagues at the same time.  Confidence up front, pressure from behind, the engine is up and running.

Harrison can also take inspiration from his own brother, Christian, who lost in the first round after having to earn a place in the draw in the qualifying rounds (as did Ryan). Christian, who is 22, has been under the surgeon’s knife seven times already and has not stopped wanting to be a champion.

He is that already.