UK light heavyweight Joshua Buatsi secured a victory yet underwhelming start to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a close ten-round fight at the Manchester venue.
But the challenger landed significant shots, delivering effective individual punches in a match where the approaches didn't complement each other, with frequent clinching spoiling the contest.
Two judges judged it 96-94 to Buatsi, with the third a even score.
"It wasn't my best showing but how do champions respond? They win," the victor stated in the ring as he was greeted with disapproval from the audience.
The Londoner got back to winning after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers believed Parker, 31, should have been awarded the victory but the contender endured the second loss of his 28-bout career.
Buatsi Earns Win in Slow Encounter
His career development has plateaued in recent times through promotional disputes and long spells of inactivity.
Once tipped as the future of British boxing, he now stands trying to realize his potential - possibly in what feels like a ultimate opportunity - under recent support.
He opened tentatively, with both competitors willing to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was making just his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a solid defense to edge the better stanzas.
The audience's tolerance wore thin during regular grabbing, with Parker going down several times during grappling.
The underdog ended stronger, but multiple periods were challenging to assess. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Memorial Motivates All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a terrific all-Manchester fight to capture the European light-heavyweight belt.
The arena grew hushed for a extremely emotional memorial prior to the bout as ten bells tolled in honor of the city's native Hatton, who passed away at age 46 in September.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the last bell ended, the silence gave way to a shout of "there's just one Ricky Hatton".
The fighting inside the ropes equaled the sentiment. The eventual winner was floored by a significant blow directly to the chin in the initial stage, rising shakily to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was damaged quickly, heavy swelling developing under his eye as the duo traded hard punches.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the intensity hardly diminished over 12 rounds.
The victor narrowly won the result with official scores of 114-114, 115-113 and clearer margin, but each competitor were relentless and full of heart, exactly what their inspiration the legend embodied.
