UK light heavyweight Joshua Buatsi earned a win yet unimpressive debut to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective clean blows in a match where the styles never quite clicked, with excessive holding disrupting the contest.
The scoring judges judged it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my finest display but how do champions respond? They succeed," the victor stated in the ring as he was met by negative reactions from the audience.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the victory but the British boxer suffered the second defeat of his 28-fight career.
The Champion Secures Victory in Dull Affair
The fighter's advancement has stalled in recent times through promotional disputes and long spells of inactivity.
Once tipped as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what appears to be a last chance - under fresh management.
He opened tentatively, with both competitors willing to take risks in a calculated early stages.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after breaking his hand mid-fight, was participating in his second fight at the higher weight class.
By the middle rounds, the underdog had made it competitive, making life awkward for Buatsi, who utilized a tight guard to edge the better rounds.
The audience's tolerance wore thin during regular grabbing, with Parker falling to the floor multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - working with Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi progresses, but with the likes of hard hitter Benavidez, and Russian star Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Inspires Local Rivalry Battle
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a excellent local rivalry contest to secure the continental championship.
The venue fell silent for a extremely emotional memorial prior to the bout as a bell ceremony rang in memory of Manchester's own Hatton, who died aged 46 in recently.
It was the first major televised fight night in the city since the passing of Hatton. As the concluding sound faded, the quiet became a chant of "there's only one Hatton".
The competition during the bout equaled the feeling. The eventual winner was sent to the canvas by a left hook squarely on the chin in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up soon, significant bruising appearing under his eye as the duo landed powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur barely secured the verdict with scoring tallies of 114-114, narrow lead and 115-112, but the two athletes were persistent and brave, exactly what their idol Hatton stood for.
