British light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to life under new promoters with a points victory over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a split decision in a close ten-round contest at the Manchester venue.
But the challenger landed significant shots, landing some telling single shots in a fight where the styles never quite clicked, with constant grabbing spoiling the fight.
The scoring judges scored it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor said in the ring as he was faced disapproval from the audience.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts believed Parker, 31, merited the decision but the contender endured the second loss of his 28-bout professional journey.
The Champion Secures Win in Dull Match
Buatsi's progress has slowed in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what seems like a last chance - under recent support.
He opened tentatively, with the two boxers prepared to be aggressive in a calculated initial rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who operated with a tight guard to narrowly win the better stanzas.
The audience's tolerance diminished during constant clinching, with the challenger slipping to the canvas multiple occasions during grappling.
Parker ended stronger, but multiple periods were hard to judge. However, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to secure the continental belt.
The arena grew hushed for a extremely emotional homage before the fight as ten bells sounded in remembrance of Manchester's own Hatton, who passed away aged 46 in recently.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the final chime disappeared, the stillness became a shout of "only one Hatton".
The competition inside the ropes matched the sentiment. The eventual winner was floored by a powerful punch flush on the face in the early round, getting up unsteadily to his feet on the eight count.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, Rea - in rival City blue - was marked up quickly, significant bruising forming under his orbital area as the duo traded powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor edged the result with judges scorecards of draw, close margin and 115-112, but each competitor were determined and brave, all the qualities their hero the legend stood for.
