UK light heavyweight Joshua Buatsi made a winning yet unimpressive beginning to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a tight ten-round bout at the boxing arena.
But the challenger had his moments, delivering effective clean blows in a fight where the approaches didn't complement each other, with frequent clinching marring the contest.
The officials scored it 96-94 for to Buatsi, with the third a even score.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the ring as he was faced boos from the audience.
The British fighter returned to winning ways after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Various analysts thought the challenger, 31, merited the win but the Derbyshire fighter experienced the second loss of his 28-bout professional journey.
Buatsi Claims Win in Uneventful Affair
Buatsi's progress has slowed in recent years through contract problems and extended periods of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to realize his potential - perhaps in what feels like a ultimate opportunity - under recent support.
He began cautiously, with the two boxers prepared to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand in the contest, was making just his second bout at light heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for the favorite, who utilized a tight guard to narrowly win the better periods.
The crowd's patience diminished during frequent holding, with the challenger going down several times during grappling.
The underdog finished the stronger, but multiple periods were hard to judge. However, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry contest to secure the continental title.
The arena fell silent for a extremely emotional tribute prior to the bout as a bell ceremony sounded in remembrance of Manchester's own Ricky Hatton, who died aged 46 in September.
It was the first major televised match card in the city since the passing of Hatton. As the last bell ended, the stillness transitioned to a shout of "only one Hatton".
The fighting within the ring reflected the emotion. The eventual winner was knocked down by a left hook squarely on the jaw in the early round, getting up unsteadily to his position on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was marked up early, noticeable damage developing under his face as the duo traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the action seldom decreased over the full distance.
Arthur narrowly won the result with scoring tallies of even score, close margin and 115-112, but the two athletes were relentless and full of heart, everything their inspiration the legend embodied.
