British light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a tight 10-round bout at the boxing arena.
But the challenger found success, landing some telling individual punches in a contest where the approaches didn't complement each other, with frequent clinching marring the action.
The scoring judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best display but what defines champions? They succeed," the victor said in the ring as he was met by disapproval from the audience.
The British fighter got back to winning after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Several boxing experts thought the challenger, 31, should have been awarded the decision but the Derbyshire fighter endured the second defeat of his 28-match career.
The Champion Earns Triumph in Uneventful Match
Buatsi's progress has stalled in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the future of British boxing, he now stands trying to achieve expectations - maybe in what seems like a last chance - under new promotional backing.
He opened tentatively, with the two boxers willing to be aggressive in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was making just his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who utilized a solid defense to edge the more effective rounds.
The audience's tolerance wore thin because of constant clinching, with Parker going down various instances during clinches.
Parker closed well, but several stanzas were hard to judge. However, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
The victor progresses, but with the likes of power puncher Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Tribute Fuels All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a excellent local rivalry battle to capture the continental championship.
The venue became quiet for a deeply poignant memorial prior to the bout as ten bells tolled in remembrance of local hero Hatton, who died 46 years old in September.
It was the first major televised fight night in the urban center since the passing of Hatton. As the final chime faded, the quiet became a chant of "there's just one Ricky Hatton".
The action inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the chin in the second round, getting up unsteadily to his feet on the count of eight.
But the Manchester United-red attire of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was injured quickly, noticeable damage forming under his face as the duo landed powerful shots.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the pace rarely dropped over 12 rounds.
The victor narrowly won the decision with scoring tallies of 114-114, close margin and clearer margin, but the two athletes were persistent and brave, everything their inspiration the legend represented.
