PARIS — The crooked tennis players knew him as “Maestro.” To European investigators, the Armenian based in Belgium is emerging as the suspected ringleader of an organized gambling syndicate suspected of fixing hundreds of matches and paying off more than 100 players from around Europe.

As Roger Federer and other stars at the top of tennis compete in the Australian Open, players far lower down the sport’s food chain are being questioned this week by police in France on suspicion of fixing matches for Grigor Sargsyan, 28-year-old known as the Maestro, investigators said. Sargsyan is being held in a Belgian jail.

The picture emerging from months of digging by police working across Europe is of a massive match-fixing scheme, organized via encrypted messaging, involving dozens of low-ranked players in small tournaments with little prize money. Police say Sargsyan employed mules, people hired for a few euros (dollars) to place bets for the syndicate that were small enough to slip under the radar of gambling watchdogs.

Sources close to the investigation, all speaking on condition of anonymity because they weren’t authorized to discuss details publicly, said four French players were in police custody on Wednesday and at least one of them told investigators that he fixed around two dozen matches for Sargsyan.

They named the players as Jules Okala, 21; Mick Lescure, 25; Yannick Thivant, 31; and Jerome Inzerillo, 28. None operated in the highest spheres of tennis. The career-best singles ranking of any of them was 354, reached by Inzerillo in 2012. The arrests of Okala and Lescure were first reported Wednesday by French sports newspaper L’Equipe.

A dozen or more other French players are expected to be questioned in coming weeks. An investigator said France was one of the countries “hardest hit” by the syndicate, which targeted lower-level pro tournaments. Okala and Lescure were detained before they were to play in a modest tournament in Bressuire, western France, this week that offers a total of $15,000 in prize money.

Investigators have also questioned players in Belgium, the Netherlands, Germany, Slovakia, and Bulgaria and are looking to question others, including both players and managers, in the United States, Chile and Egypt.

In all, more than 100 players are suspected of having worked with the syndicate, fixing matches, sets or games in exchange for payments of 500 to 3,000 euros ($570 to $3,400).

“The impression we’re getting is that it is very commonplace,” one official told The Associated Press. Another said several hundred matches are thought to have been fixed.

Investigators fear that players used by the syndicate could suck others into the scheme and could go on to infect bigger tournaments if they climb higher in the rankings.

“In time, they could be managers of other new players or trainers so we have to get them out of the system, or they could corrupt others in a few years,” one official told The Associated Press.

Sargsyan was swept up in a wave of arrests in Belgium last June and faces organized crime, match fixing, money laundering and forgery charges. A suspected banker for the syndicate also faces money laundering and organized crime charges, while four others are being investigated for illegal gambling and finding mules, who are thought to have been paid for placing modest bets for the syndicate on matches that it fixed.

Because the bets were small, the risk of detection was “almost zero,” but the profits could still be considerable if many bets were placed, one official said.

Still unclear is whether the Belgium-based syndicate was linked to another match-fixing and gambling operation, also involving Armenians, unraveled in Spain . Spanish police last week announced that 28 professional tennis players, including one who participated in last year’s U.S. Open, were linked to that ring, taking bribes to fix results that the group bet on using fake identities.

MELBOURNE, Australia — If this was it for Andy Murray, if this truly was it, he gave himself — and an appreciative, raucous crowd that included his mother and brother — quite a gutsy goodbye, the type of never-give-in performance he’s famous for.

What Murray could not quite do Monday at the Australian Open was finish off a stirring comeback and prolong what might just be the final tournament of his career.

Playing on a surgically repaired right hip so painful that pulling on socks is a chore, he summoned the strength and strokes to erase a big deficit and force a fifth set before eventually succumbing to 22nd-seeded Roberto Bautista Agut 6-4, 6-4, 6-7 (5), 6-7 (4), 6-2, Murray’s first opening-round loss at a Grand Slam tournament in 11 years.

“If today was my last match, look, it was a brilliant way to finish,” Murray said. “I literally gave everything that I had on the court, fought as best as I could, and performed a lot better than what I should have done with the amount I’ve been able to practice and train.”

Murray, just 31, is a year removed from his operation, and he said that he will decide in the next week or so whether to have a second one. If he opts to avoid another procedure, he might be able to play in July at Wimbledon, where he won two of his three major titles, including the first for a British man in 77 years. If he decides for further surgery, then Monday’s match might have been his last.

Even with a hitch in his gait, even as he leaned forward to rest his hands on his knees between points, Murray summoned the strength and the strokes to push the match beyond the 4-hour mark.

And the fans tried to will him past Bautista Agut, who had lost in straight sets all three previous matches the two men had played.

They roared when Murray managed to break back to 2-all on the way to taking the third set, with his mom, Judy, smiling widely as she stood alongside other spectators.

They chanted his name when he grabbed the fourth set.

They rose when the compelling contest ended.

“Andy deserves this atmosphere. Andy deserves (that) all the people came to watch him,” Bautista Agut said. “He’s a tough, tough fighter. A tough opponent. He gives everything until the last point. I want to congratulate him for all he did for tennis.”

Afterward, a video was shown in the stadium with tributes to Murray from various players, including rivals Roger Federer, Rafael Nadal and Novak Djokovic, along with Nick Kyrgios, Caroline Wozniacki, Karolina Pliskova and Sloane Stephens.

“Amazing career. Congratulations, buddy,” Federer said. “I’m your biggest fan.”

Federer opened his bid for a third consecutive Australian Open championship, and record seventh overall, with a 6-3, 6-4, 6-4 victory over Denis Istomin at Rod Laver Arena. Nadal, whose 17 career majors are second among men only to Federer’s 20, overpowered Australian wild-card entry James Duckworth 6-4, 6-3, 7-5 earlier.

Nadal, who had surgery on his right ankle in November, hadn’t competed since stopping during his U.S. Open semifinal in September because of a bad knee.

“It’s very difficult to start (again) after an injury,” Nadal said. “I know it very well.”

Other major title winners who advanced on Day 1, when the temperature approached 90 degrees (33 Celsius), included defending champion Caroline Wozniacki, Maria Sharapova — who beat Harriet Dart 6-0, 6-0 — Angelique Kerber, Sloane Stephens and Petra Kvitova.

The highest-seeded player to exit was No. 9 John Isner, who hit 47 aces but lost 7-6 (4), 7-6 (6), 6-7 (4), 7-6 (5) against 97th-ranked Reilly Opelka in an all-American match.

The most attention, though, was drawn by Murray, who is as popular for his success on the court as his attitude away from it.

The stands were dotted with British and Scottish flags and with signs of support. When Bautista Agut entered, he was greeted by a smattering of polite applause. When Murray was introduced, there were full-throated screams, followed by chants of his first name.

As play began, Murray delighted his well-wishers every so often with terrific shots on a full sprint and his trademark, quick-reflex returns. When he flubbed a shot or otherwise let a point slide by, Murray displayed the muttering and leg-slapping self-contempt the world has come to know and expect — and, let’s face it, love — from the guy.

For all that Murray accomplished over the years, including reaching No. 1 in the rankings and a pair of Olympic singles gold medals, he never was able to leave Melbourne with the trophy, finishing as the runner-up five times.

When Murray eventually succumbed to his weariness — not to mention Bautista Agut — the arena speakers blared Queen’s “We are the Champions,” with its fitting line: “And we’ll keep on fighting ’til the end.”

If this was, indeed, the end, Murray did just that.

“I’d be OK,” he said, “with that being my last match.”