UK light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a close ten-round contest at the boxing arena.
But the challenger found success, landing some telling clean blows in a contest where the techniques never quite clicked, with frequent clinching marring the fight.
Two judges had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They prevail," Buatsi said in the ring as he was met by negative reactions from the audience.
The Londoner bounced back after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Some ringside observers believed Parker, thirty-one, merited the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
The Champion Claims Win in Uneventful Affair
The fighter's advancement has slowed in recent years through management issues and long spells of lack of fights.
Once tipped as the future of the British fight scene, he now is positioned trying to achieve expectations - possibly in what feels like a last chance - under recent support.
He opened tentatively, with the two boxers ready to be aggressive in a calculated initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second appearance at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a tight guard to barely take the better stanzas.
The spectators' acceptance diminished during constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
Parker closed well, but multiple periods were challenging to assess. Although, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Hatton Tribute Motivates All-Manchester Contest
In the co-main event, Arthur overcame Bradley Rea by split-decision in a excellent local rivalry contest to capture the continental title.
The stadium grew hushed for a profoundly moving homage before the fight as a bell ceremony tolled in remembrance of the city's native Hatton, who passed away aged 46 in September.
It was the first major televised fight night in the location since Hatton's death. As the final chime faded, the quiet became a shout of "there's just one Ricky Hatton".
The competition within the ring reflected the feeling. Arthur was knocked down by a significant blow squarely on the jaw in the initial stage, rising shakily to his feet on the eight count.
But the red-colored equipment of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was injured quickly, heavy swelling appearing under his orbital area as the duo traded powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur narrowly won the verdict with judges scorecards of draw, narrow lead and wider gap, but the two athletes were determined and full of heart, all the qualities their idol Hatton represented.
