UK light heavyweight Joshua Buatsi made a winning yet unimpressive beginning to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a majority decision in a tight 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a fight where the techniques failed to mesh, with excessive holding spoiling the contest.
The scoring judges scored it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They prevail," the victor stated in the ring as he was greeted with boos from the spectators.
The Londoner bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts felt Parker, thirty-one, merited the win but the British boxer suffered the second loss of his 28-match professional journey.
The Champion Secures Victory in Dull Affair
His career development has plateaued in the past few years through management issues and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to achieve expectations - possibly in what feels like a last chance - under recent support.
He began cautiously, with neither fighter willing to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after breaking his hand in the contest, was participating in his second bout at light-heavyweight.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to barely take the cleaner rounds.
The crowd's patience decreased amid constant clinching, with Parker going down various instances during clinches.
Parker ended stronger, but many rounds were challenging to assess. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Hatton Tribute Fuels Local Rivalry Fight
In the supporting bout, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to win the European light-heavyweight title.
The arena grew hushed for a deeply poignant tribute before the fight as 10 bells sounded in remembrance of Manchester's own Hatton, who passed away at age 46 in recently.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the concluding sound ended, the quiet transitioned to a roar of "only one Hatton".
The competition inside the ropes equaled the sentiment. Arthur was sent to the canvas by a left hook squarely on the chin in the early round, rising shakily to his footing on the eight count.
But the Manchester United-red attire of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged early, noticeable damage appearing under his face as the duo traded hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the pace rarely dropped over the full distance.
The victor barely secured the result with official scores of even score, close margin and clearer margin, but both fighters were relentless and full of heart, everything their hero the legend embodied.
