British light heavyweight Joshua Buatsi earned a win yet underwhelming start to his career under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a tight ten-round fight at the Manchester venue.
But Parker had his moments, delivering effective single shots in a match where the styles never quite clicked, with excessive holding disrupting the contest.
The officials had it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi stated in the arena as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Various analysts felt Parker, 31, should have been awarded the decision but the contender endured the second loss of his 28-fight career.
The Champion Claims Win in Dull Encounter
His career development has stalled in recent years through contract problems and long spells of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers willing to be aggressive in a cagey opening few rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to narrowly win the cleaner stanzas.
The audience's tolerance diminished during frequent holding, with Parker falling to the floor several times during clinches.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the caliber of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Battle
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a outstanding all-Manchester battle to secure the continental belt.
The arena became quiet for a profoundly moving homage before the fight as 10 bells sounded in memory of Manchester's own Hatton, who died aged 46 in recently.
It was the first major televised match card in the city since the passing of Hatton. As the concluding sound faded, the silence transitioned to a shout of "only one Ricky Hatton".
The competition during the bout matched the sentiment. The eventual winner was knocked down by a left hook directly to the face in the second round, standing uncertainly to his footing on the count of eight.
But the red-colored equipment of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was damaged quickly, noticeable damage developing under his face as the duo traded punishing blows.
The challenger, 27, landed power punches but the champion, 34, responded in kind with effective uppercuts as the pace rarely dropped over 12 rounds.
The victor barely secured the result with scoring tallies of even score, narrow lead and wider gap, but the two athletes were determined and courageous, all the qualities their hero Hatton represented.
