British light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a tight ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a fight where the techniques failed to mesh, with constant grabbing marring the contest.
The officials judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my finest display but how do champions respond? They prevail," the victor commented in the arena as he was faced negative reactions from the spectators.
The Londoner got back to winning after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts thought the challenger, 31, should have been awarded the win but the British boxer experienced the second setback of his 28-fight career.
Buatsi Secures Win in Slow Match
His career development has stalled in the past few years through promotional disputes and extended periods of lack of fights.
Earlier forecast as the next star of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a ultimate opportunity - under fresh management.
He started carefully, with both competitors willing to be aggressive in a tentative initial rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was participating in his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who operated with a protective stance to barely take the cleaner rounds.
The crowd's patience decreased during constant clinching, with Parker falling to the floor multiple occasions during grappling.
The underdog closed well, but many rounds were hard to judge. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a terrific local rivalry contest to win the European light heavyweight belt.
The venue fell silent for a deeply poignant memorial prior to the bout as a bell ceremony rang in remembrance of Manchester's own Hatton, who died at age 46 in last month.
It was the first major televised fight night in the location since Hatton's death. As the last bell disappeared, the stillness gave way to a roar of "there's only one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was floored by a powerful punch flush on the jaw in the early round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was marked up early, heavy swelling developing under his face as the duo traded powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the pace rarely dropped over twelve rounds.
Arthur barely secured the result with scoring tallies of draw, 115-113 and clearer margin, but both fighters were relentless and full of heart, everything their inspiration Hatton represented.
