British light heavyweight Joshua Buatsi made a winning yet unimpressive start to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight 10-round contest at the boxing arena.
But the challenger landed significant shots, delivering effective clean blows in a match where the styles never quite clicked, with constant grabbing marring the fight.
Two judges scored it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my finest showing but how do champions respond? They win," Buatsi commented in the arena as he was met by disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the win but the British boxer experienced the second loss of his 28-match career.
The Champion Earns Win in Dull Match
The fighter's advancement has slowed in recent times through contract problems and considerable time of inactivity.
Once tipped as the next star of British boxing, he now stands trying to achieve expectations - perhaps in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors ready to take risks in a calculated early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was competing in only his second bout at light heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who utilized a tight guard to edge the more effective stanzas.
The audience's tolerance diminished amid constant clinching, with the challenger slipping to the canvas several times during grappling.
The underdog finished the stronger, but many rounds were hard to judge. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent local rivalry contest to secure the European light heavyweight belt.
The stadium became quiet for a profoundly moving tribute prior to the bout as a bell ceremony rang in memory of local hero Hatton, who died aged 46 in last month.
It was the first major televised boxing event in the city since Hatton's death. As the last bell faded, the quiet gave way to a shout of "only one Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was knocked down by a significant blow flush on the jaw in the second round, getting up unsteadily to his footing on the eight count.
But the red-colored attire of Arthur soon advanced again. Across the ring, the opponent - in opposing blue - was injured early, noticeable damage developing under his orbital area as the pair traded punishing blows.
The challenger, 27, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the action seldom decreased over 12 rounds.
The victor narrowly won the result with scoring tallies of draw, 115-113 and wider gap, but each competitor were determined and full of heart, exactly what their inspiration the legend stood for.
