Meritocracy goes only so far at the U.S. Open. To start this year's tournament, defending champion Marin Cilic and 2014 runner-up Kei Nishikori were asked to play Monday on the second-tier show court, leaving Arthur Ashe Stadium's center court to more glamorous names in the afternoon.

It was a reminder that last year's title match was something of an aberration -- no Djokovic, no Federer, no Nadal, no Murray. And further proof of elite sports' "what have you done lately?" soul.

Especially when Nishikori, 25, the No. 4 seed from Japan, promptly lost before a less-than-capacity crowd at 10,000- seat Louis Armstrong Stadium. He was followed at Armstrong by Croatia's Cilic, who began his match before an intimate gathering of barely 3,000, defeating a qualifier ranked a humble 94th in the world.

U.S. OpenU.S. Open: Men's results

That small assembly, which grew slightly as the match unfolded, belied Cilic's championship status and the record first-day crowd of 37,601 on the National Tennis Center grounds. And, for Cilic's postmatch news conference, there were a mere three reporters in the 150-seat interview room.

"Well,'' Cilic said diplomatically, "it was a pretty nice crowd for a hot day. It was pretty humid, and the match before went five sets. The crowd also needs some refreshments.''

Nishikori's 6-4, 3-6, 4-6, 7-6, (8-6) 6-4 loss to Frenchman Benoit Paire, ranked 41st, marked the first time in 24 years that an Open runner-up lost his first match the next year. (Andre Agassi, beaten in the 1990 final by Pete Sampras, lost to Aaron Krickstein in his first '91 match.)

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Nishikori had a match point in the fourth-set tiebreaker, "but I kind of lost a little bit [on] my forehand,'' he said. "I mean, tiebreak can go both ways, so maybe I lost a little bit of concentration . . . thinking too much.

"It's very sad to lose in the first round, but he's a good player. I think it was more because of him that I wasn't playing 100 percent.''

Cilic had a far better experience, a 6-3, 7-6 (7-3), 7-6 (7-3) win over Guido Pella of Argentina.

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It should be noted that both Nishikori and Cilic, since our last Open episode, have provided reminders of relentless change. That fits the National Tennis Center's state of doubling as a construction site -- the retractable roof slowly materializing over Ashe Stadium and a new Grandstand emerging.

Cilic, who missed January's Australian Open with a shoulder injury, made only the fourth round in the French Open and the quarters at Wimbledon. Nishikori, after quarterfinal runs at the Australian and French, lost in Wimbledon's second round.

But at least top-seeded Novak Djokovic, favored to add another title to his nine major victories, demonstrated a familiar sense of order in dismissing Brazilian Joao Souza, ranked 91st, in straight sets, 6-1, 6-1, 6-1.

Nadal wins. Eighth-seeded Rafael Nadal of Spain beat Croatia's Borna Coric, 6-3, 6-2, 4-6, 6-4. Nadal missed last year's Open because of a wrist injury. He won the tournament in 2010 and 2013.

Germany's Tommy Haas, in his 17th U.S. Open, lost to Spaniard Fernando Verdasco in five sets; No. 7 seed David Ferrer of Spain defeated Radu Albot of Moldova; No. 10 Milos Raonic of Canada beat American Tim Smyczek and No. 17 Grigor Dimitrov of Bulgaria defeated qualifier Matthew Ebden of Australia.