The Sharks burst Manly's bubble with some dazzling tries on Friday night, but the sight of Brailey trudging off midway through the second half was a major blow for his club and state.
The NSW super sub will await the result of scans on Saturday before learning his fate ahead of State of Origin II in Melbourne on June 17.
"He's dejected, obviously," said Sharks coach Craig Fitzgibbon.
"But he's not going to be out forever. If it is a fracture, hopefully it's clean and not displaced, so that would minimise the time (out). That's what it's looking like."
With his superstar halves partner Nicho Hynes sidelined with a calf strain, Braydon Trindall delivered a playmaking masterclass to pilot the Sharks to back-to-back wins for only the second time in 2026.
Trindall bagged one try and had a hand or boot in three others as Cronulla wowed their home fans at Ocean Protect Stadium.
Until being injured, Brailey and his NSW teammate Addin Fonua-Blake were also superb backing up from the Blues' thrilling series-opening win over Queensland on Wednesday night.
Back-rower Billy Burns - starting after Maroons bench forward Briton Nikora sat out the contest - also shone with a rousing try-scoring double as Cronulla jumped from ninth to seventh on the table, only behind Manly on points differential.
Manly's only defeat in eight previous matches since Foran took over from Anthony Siebold before round five was a two-point loss to Penrith.
The Sea Eagles had boasted the best attack and defence in the league under the rookie coach and club legend.
But without their Origin stars Tolu Koula and Haumole Olakau'atu, they looked a different side and trailed 22-4 at halftime.
"We missed the mark completely in that first 40. We got taught a good lesson tonight," Foran said.
"We missed the physical battle. They did to us what we've been able to do to sides over the past eight weeks.
"And they made it happen. They turned up with the attitude, ready to make it happen, and we just missed the jump badly."
Manly had only conceded an average of 13.7 points a game under Foran, but Cronulla eclipsed that total in barely half an hour.
In a dream debut, 24-year-old halfback Niwhai Puru - deputising for Hynes - opened the scoring when he backed up a brilliant dummy-half burst from Brailey in the eighth minute.
Up 8-0, it was all the Sharks before Manly finally enjoyed some possession and field position, and fullback Clayton Faulalo broke through to cash in on a series of repeat sets to put the visitors on the board.
Teig Wilton ran a beautiful line off Trindall and showed great footwork to bag Cronulla's second try, before Trindall blew the game open in the final moments of the first half.
First Burns pounced on Trindall's probing kick that had been executed for Ronaldo Mulitano.
Then Burns reeled in another Trindall kick across field after the halftime siren to break Manly fans' hearts and extend the Sharks' lead to 18 points.
Trindall looked to have sealed the deal with a solo strike early in the second half, but kept Manly in the game with three missed conversions.
The Sea Eagles threatened to snatch victory late with tries to Ben Trbojevic, Jason Saab and Jamal Fogarty, but the Sharks hung on.
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