UK light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a competitive 10-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a contest where the approaches failed to mesh, with constant grabbing marring the contest.
Two judges had it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my finest display but what defines champions? They succeed," the victor commented in the ring as he was faced boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th career victory.
Some ringside observers believed Parker, 31, merited the victory but the British boxer endured the second setback of his 28-match career.
Buatsi Earns Triumph in Dull Encounter
Buatsi's progress has stalled in recent times through contract problems and considerable time of lack of fights.
Once tipped as the future of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter willing to be aggressive in a calculated early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, making life awkward for Buatsi, who utilized a protective stance to narrowly win the better rounds.
The spectators' acceptance wore thin because of frequent holding, with Parker falling to the floor multiple occasions during grappling.
Parker closed well, but multiple periods were difficult to score. However, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of heavy hitter Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Hatton Tribute Fuels Manchester Derby Fight
In the co-main event, Arthur defeated Rea by split-decision in a outstanding local rivalry contest to secure the European light-heavyweight title.
The stadium became quiet for a extremely emotional memorial ahead of the contest as a bell ceremony tolled in remembrance of Manchester's own Hatton, who passed away at age 46 in September.
It was the first major televised boxing event in the urban center since Hatton's death. As the concluding sound disappeared, the quiet became a shout of "there's just one Hatton".
The competition inside the ropes matched the emotion. Arthur was floored by a significant blow flush on the jaw in the early round, getting up unsteadily to his feet on the eight count.
But the traditional red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged soon, noticeable damage developing under his eye as the fighters landed hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the verdict with official scores of even score, close margin and clearer margin, but each competitor were determined and courageous, all the qualities their idol the legend embodied.
