British light-heavyweight Joshua Buatsi made a winning yet unimpressive beginning to his career under new promoters with a points victory over Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a split decision in a close 10-round bout at the Manchester venue.
But the challenger landed significant shots, landing some telling individual punches in a match where the techniques never quite clicked, with constant grabbing marring the action.
The scoring judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest performance but how do champions respond? They prevail," the victor stated in the ring as he was faced boos from the spectators.
The Londoner bounced back after his first professional defeat - an memorable fight with his previous opponent in February - to secure a 20th career victory.
Several boxing experts thought the challenger, 31, merited the win but the British boxer experienced the second setback of his 28-fight career.
Buatsi Claims Victory in Dull Affair
His career development has slowed in the past few years through contract problems and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to achieve expectations - maybe in what seems like a last chance - under recent support.
He opened tentatively, with both competitors prepared to take risks in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second bout at light-heavyweight.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who worked behind a solid defense to narrowly win the more effective rounds.
The crowd's patience decreased because of constant clinching, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog closed well, but many rounds were hard to judge. Although, former world champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Motivates Manchester Derby Fight
In the co-main event, Arthur beat Bradley Rea by close verdict in a excellent all-Manchester fight to win the continental belt.
The venue grew hushed for a profoundly moving memorial before the fight as ten bells tolled in memory of the city's native Ricky Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast fight night in the urban center since Hatton's passing. As the final chime ended, the quiet gave way to a roar of "there's only one Hatton".
The action inside the ropes reflected the emotion. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the early round, rising shakily to his footing on the referee's count.
But the traditional red attire of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was injured quickly, significant bruising developing under his orbital area as the pair exchanged powerful shots.
The challenger, 27, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the action hardly diminished over 12 rounds.
The victor narrowly won the decision with scoring tallies of even score, close margin and clearer margin, but both fighters were relentless and full of heart, all the qualities their inspiration Hatton represented.
