UK light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a contest where the approaches didn't complement each other, with frequent clinching marring the action.
The officials judged it 96-94 for to Buatsi, 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 faced negative reactions from the crowd.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Several boxing experts believed Parker, thirty-one, merited the victory but the contender endured the second setback of his 28-match career.
Buatsi Secures Win in Dull Match
Buatsi's progress has stalled in recent years through management issues and long spells of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter prepared to be aggressive in a tentative opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was participating in his second appearance at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who operated with a protective stance to barely take the cleaner stanzas.
The spectators' acceptance wore thin amid regular grabbing, with the challenger falling to the floor several times during close exchanges.
Parker ended stronger, but multiple periods were challenging to assess. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of heavy hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Fight
In the co-main event, Arthur overcame Bradley Rea by split-decision in a outstanding all-Manchester fight to win the European light-heavyweight championship.
The venue fell silent for a profoundly moving tribute prior to the bout as a bell ceremony sounded in honor of local hero Hatton, who passed away aged 46 in last month.
It was the first major televised fight night in the city since Hatton's death. As the concluding sound disappeared, the stillness became a shout of "there's only one Hatton".
The competition within the ring equaled the feeling. The eventual winner was floored by a left hook squarely on the face in the second round, standing uncertainly to his feet on the eight count.
But the traditional red attire of Arthur soon pressed ahead again. Across the ring, Rea - in rival City blue - was marked up quickly, significant bruising forming under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur edged the decision with judges scorecards of 114-114, narrow lead and clearer margin, but both fighters were persistent and courageous, everything their idol Hatton represented.
