UK light-heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a competitive 10-round bout at the boxing arena.
But the challenger had his moments, connecting with powerful clean blows in a match where the techniques failed to mesh, with constant grabbing spoiling the contest.
The officials judged it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but what do champions do? They win," the victor said in the ringside as he was met by boos from the spectators.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers felt the challenger, 31, should have been awarded the win but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
The Champion Claims Win in Slow Affair
Buatsi's progress has slowed in recent times through management issues and considerable time of inactivity.
Earlier forecast as the future of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what appears to be a last chance - under recent support.
He opened tentatively, with the two boxers willing to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for Buatsi, who operated with a solid defense to barely take the more effective periods.
The audience's tolerance wore thin during constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
Parker closed well, but multiple periods were hard to judge. Although, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding all-Manchester fight to secure the continental title.
The venue fell silent for a profoundly moving homage before the fight as a bell ceremony tolled in remembrance of local hero Ricky Hatton, who passed away at age 46 in recently.
It was the premier televised match card in the location since Hatton's passing. As the concluding sound faded, the stillness transitioned to a chant of "only one Hatton".
The fighting within the ring reflected the sentiment. Arthur was knocked down by a powerful punch squarely on the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the traditional red equipment of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up soon, heavy swelling forming under his face as the duo exchanged hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity seldom decreased over 12 rounds.
The victor barely secured the verdict with judges scorecards of 114-114, close margin and 115-112, but each competitor were determined and full of heart, exactly what their hero the legend represented.
