British light heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's punch output likely gained him a split decision in a tight 10-round bout at the Manchester venue.
But the challenger landed significant shots, delivering effective clean blows in a contest where the approaches failed to mesh, with frequent clinching marring the action.
The officials judged it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my best performance but what defines champions? They prevail," the victor stated in the ring as he was met by boos from the audience.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th career victory.
Various analysts felt the challenger, thirty-one, should have been awarded the victory but the British boxer endured the second defeat of his 28-fight career.
Buatsi Secures Triumph in Dull Affair
The fighter's advancement has stalled in recent times through management issues and considerable time of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what seems like a last chance - under new promotional backing.
He opened tentatively, with both competitors prepared to take risks in a calculated early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who utilized a protective stance to narrowly win the better periods.
The crowd's patience diminished during frequent holding, with the challenger slipping to the canvas multiple occasions during grappling.
Parker closed well, but multiple periods were hard to judge. However, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor advances, but with the likes of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a terrific local rivalry fight to win the European light heavyweight belt.
The venue became quiet for a deeply poignant memorial ahead of the contest as ten bells sounded in honor of local hero Hatton, who passed away 46 years old in September.
It was the premier televised match card in the city since Hatton's death. As the concluding sound disappeared, the quiet gave way to a shout of "there's just one Hatton".
The action inside the ropes reflected the sentiment. The eventual winner was floored by a left hook directly to the face in the second round, rising shakily to his feet on the count of eight.
But the traditional red attire of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was damaged early, noticeable damage appearing under his face as the fighters exchanged powerful shots.
Rea, 27, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the action rarely dropped over twelve rounds.
Arthur edged the result with scoring tallies of 114-114, narrow lead and clearer margin, but both fighters were persistent and brave, everything their hero Hatton embodied.
