British light-heavyweight Joshua Buatsi made a winning yet unimpressive start to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a competitive ten-round bout at the boxing arena.
But Parker found success, landing some telling single shots in a fight where the techniques didn't complement each other, with constant grabbing disrupting the fight.
The scoring judges scored it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my finest performance but what do champions do? They succeed," the victor said in the ring as he was greeted with disapproval from the audience.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in February - to secure a 20th career victory.
Various analysts felt Parker, 31, deserved the win but the Derbyshire fighter experienced the second defeat of his 28-fight professional journey.
Buatsi Earns Victory in Uneventful Match
The fighter's advancement has slowed in recent times through promotional disputes and extended periods of lack of fights.
Once tipped as the future of British boxing, he now finds himself trying to realize his potential - possibly in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors willing to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who utilized a tight guard to narrowly win the better stanzas.
The audience's tolerance decreased amid constant clinching, with Parker slipping to the canvas several times during close exchanges.
The underdog finished the stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, scoring for Buatsi just one round.
The victor progresses, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Motivates All-Manchester Contest
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a outstanding local rivalry fight to capture the continental title.
The arena became quiet for a extremely emotional memorial prior to the bout as a bell ceremony tolled in remembrance of Manchester's own Ricky Hatton, who succumbed 46 years old in recently.
It was the first major televised match card in the city since the passing of Hatton. As the last bell ended, the silence became a shout of "there's only one Ricky Hatton".
The fighting inside the ropes matched the emotion. Arthur was sent to the canvas by a powerful punch squarely on the face in the early round, standing uncertainly to his footing on the referee's count.
But the traditional red attire of Arthur soon came forward again. Across the ring, Rea - in competitive blue - was damaged early, heavy swelling appearing under his eye as the duo exchanged punishing blows.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, matched the intensity with effective uppercuts as the action seldom decreased over twelve rounds.
Arthur barely secured the result with official scores of 114-114, narrow lead and clearer margin, but both fighters were determined and courageous, exactly what their hero Hatton stood for.
