UK light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight ten-round contest at the Manchester venue.
But the challenger landed significant shots, delivering effective single shots in a contest where the styles never quite clicked, with frequent clinching marring the action.
The scoring judges scored it 96-94 for to the winner, with the final judge a even score.
"It wasn't my finest display but what defines champions? They prevail," Buatsi stated in the ringside as he was faced disapproval from the crowd.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to earn a 20th pro success.
Various analysts felt the challenger, 31, deserved the win but the contender suffered the second loss of his 28-bout professional journey.
The Champion Secures Triumph in Slow Encounter
His career development has slowed in recent years through management issues and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now finds himself trying to realize his potential - perhaps in what feels like a last chance - under recent support.
He began cautiously, with neither fighter prepared to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for Buatsi, who utilized a protective stance to edge the cleaner rounds.
The audience's tolerance diminished because of frequent holding, with the challenger falling to the floor various instances during grappling.
Parker finished the stronger, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor moves on, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Tribute Motivates Local Rivalry Contest
In the co-main event, Arthur overcame Bradley Rea by close verdict in a outstanding Manchester vs Manchester contest to capture the European light heavyweight championship.
The venue fell silent for a extremely emotional tribute prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who passed away at age 46 in recently.
It was the first major televised boxing event in the location since the passing of Hatton. As the last bell faded, the stillness became a chant of "there's only one Ricky Hatton".
The action during the bout reflected the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the jaw in the early round, standing uncertainly to his position on the referee's count.
But the traditional red equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in rival City blue - was injured quickly, noticeable damage appearing under his orbital area as the pair exchanged powerful shots.
Rea, 27, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the result with official scores of draw, narrow lead and clearer margin, but the two athletes were relentless and courageous, everything their inspiration Hatton represented.
