Not just the favorites have expectations. Especially at this stage of the U.S. Open, a loss is something to be mourned at all levels of the tennis caste system, by the dark horses and underdogs and long shots as well as the established royalty.

Take Jack Sock. Seeded 26th, he wasn’t supposed to beat No. 9 Jo-Wilfried Tsonga Sunday. Sock is 23 years old, never been past this point, the fourth round in a Grand Slam tournament, while Tsonga, the 31-year-old French veteran, is a five-time Slam semifinalist.

The fact that form held in Tsonga’s 6-3, 6-3, 6-7 (7), 6-2 victory did nothing to free Sock from the loser’s lament. “I felt right there with him,” Sock said. “Had chances to make it a different match. You know . . . let it slip, and against a guy like that, that’s all he needs.”

It was one of those duels that resembled old gunslinger movie scenes. Long moments of inaction as one or the other prepared to serve, eyes narrowing, sweat beading, then a sudden burst of smoke and fire. The shots were menacing and the points brief, almost all concluded with forehand winners.

Tsonga struck 26 winners with his forehand, none with his backhand. Sock’s similar totals were 20 and four. Both served consistently well, though Tsonga allowed Sock only four break-point opportunities — one of which Sock converted. Tsonga cashed six of 13 break-point attempts.

Too, Tsonga was more efficient at the net, scoring on 30 of his 41 such advances.

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So there was Sock, the last American standing in the men’s draw, whose departure meant that there still would be no U.S. man to reach the Open quarterfinals since both Andy Roddick and John Isner did in 2012.

“I’m right there,” Sock said of his improved game. “My last match was a straight-set win over a past champion here.”

But he rued the outcome the way every defeated player, regardless of ranks, does. On Saturday night, 54th-ranked Daniel Evans of Great Britain had a match point against No. 3 seed Stan Wawrinka get away for him in a five-set loss. “Whoever says you don’t think about winning the match at that point,” Evans said, “is full of it.”

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Likewise, 19-year-old qualifier Jared Donaldson felt a crucial early missed forehand tipped the match to No. 21 Ivo Karlovic. “The right shot,” he said. “I have to live with how I played it.”