UK light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to his career under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a close 10-round contest at the Co-op Live Arena.
But the challenger found success, landing some telling single shots in a fight where the approaches didn't complement each other, with constant grabbing marring the action.
The officials scored it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my finest display but what defines champions? They prevail," Buatsi commented in the ring as he was met by boos from the crowd.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers felt Parker, 31, deserved the decision but the contender suffered the second loss of his 28-bout professional journey.
The Champion Claims Win in Dull Encounter
Buatsi's progress has plateaued in the past few years through promotional disputes and considerable time of inactivity.
Once tipped as the rising talent of the British fight scene, he now is positioned trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He began cautiously, with the two boxers prepared to take risks in a cagey opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second bout at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who utilized a protective stance to narrowly win the cleaner stanzas.
The crowd's patience decreased because of regular grabbing, with the challenger falling to the floor various instances during close exchanges.
Parker finished the stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the caliber of power puncher David 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 Tribute Motivates Manchester Derby Contest
In the co-main event, Arthur beat Rea by divided decision in a excellent local rivalry battle to capture the European light heavyweight title.
The arena fell silent for a profoundly moving memorial before the fight as a bell ceremony tolled in honor of Manchester's own Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast match card in the location since Hatton's passing. As the last bell faded, the silence gave way to a shout of "there's only one Ricky Hatton".
The competition during the bout equaled the feeling. Arthur was floored by a significant blow squarely on the jaw in the early round, getting up unsteadily to his feet on the referee's count.
But the red-colored attire of the fighter soon came forward again. Across the ring, the opponent - in opposing blue - was injured early, heavy swelling developing under his orbital area as the pair exchanged powerful shots.
Rea, 27, landed power punches but Arthur, 34, fought fire with fire with powerful upward punches as the action rarely dropped over 12 rounds.
The victor edged the verdict with scoring tallies of draw, close margin and wider gap, but the two athletes were relentless and full of heart, everything their hero the legend stood for.
