British light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a close 10-round fight at the Manchester venue.
But the challenger landed significant shots, delivering effective clean blows in a fight where the styles failed to mesh, with frequent clinching disrupting the action.
The scoring judges scored it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my finest showing but how do champions respond? They win," Buatsi said in the ring as he was greeted with boos from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Several boxing experts felt the challenger, thirty-one, merited the decision but the contender experienced the second setback of his 28-fight professional journey.
Buatsi Secures Triumph in Dull Affair
Buatsi's progress has slowed in the past few years through contract problems and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors prepared to be aggressive in a calculated early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, causing problems for the favorite, who worked behind a solid defense to narrowly win the better stanzas.
The audience's tolerance decreased during frequent holding, with Parker slipping to the canvas various instances during clinches.
The underdog closed well, but several stanzas were hard to judge. However, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
The victor moves on, but with the presence of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Homage Fuels All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a excellent Manchester vs Manchester fight to capture the European light heavyweight title.
The venue grew hushed for a deeply poignant homage before the fight as a bell ceremony tolled in honor of the city's native Ricky Hatton, who died at age 46 in last month.
It was the first major televised fight night in the urban center since Hatton's passing. As the last bell disappeared, the stillness became a roar of "there's just one Ricky Hatton".
The action within the ring matched the emotion. The eventual winner was floored by a significant blow flush on the chin in the initial stage, getting up unsteadily to his footing on the eight count.
But the red-colored equipment of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was marked up early, heavy swelling forming under his eye as the fighters traded hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur narrowly won the decision with official scores of draw, narrow lead and clearer margin, but each competitor were persistent and courageous, all the qualities their inspiration Hatton stood for.
