British light heavyweight Joshua Buatsi earned a win yet disappointing debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a majority decision in a tight 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a contest where the approaches didn't complement each other, with frequent clinching disrupting the action.
The officials judged it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They prevail," the victor commented in the ringside as he was greeted with boos from the crowd.
The British fighter returned to winning ways after his maiden career setback - an epic battle with Callum Smith in February - to earn a 20th career victory.
Various analysts believed the challenger, 31, deserved the victory but the British boxer experienced the second loss of his 28-match professional journey.
The Champion Claims Victory in Uneventful Match
Buatsi's progress has stalled in recent years through contract problems and long spells of lack of fights.
Once tipped as the rising talent of the British fight scene, he now stands trying to achieve expectations - maybe in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with neither fighter ready to be aggressive in a cagey early stages.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second appearance at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to barely take the better stanzas.
The spectators' acceptance wore thin during constant clinching, with Parker slipping to the canvas multiple occasions during clinches.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just a single round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Hatton Homage Inspires Local Rivalry Fight
In the co-main event, Lyndon Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to secure the European light-heavyweight belt.
The stadium fell silent for a extremely emotional tribute prior to the bout as 10 bells tolled in honor of local hero Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the final chime disappeared, the quiet gave way to a chant of "only one Ricky Hatton".
The competition during the bout equaled the emotion. Arthur was sent to the canvas by a left hook directly to the jaw in the initial stage, getting up unsteadily to his footing on the count of eight.
But the red-colored attire of Arthur soon came forward again. Across the ring, the opponent - in competitive blue - was marked up quickly, significant bruising appearing under his face as the duo landed punishing blows.
Rea, 27, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over 12 rounds.
The victor barely secured the decision with scoring tallies of even score, close margin and wider gap, but the two athletes were relentless and full of heart, everything their hero Hatton stood for.
