UK light heavyweight Joshua Buatsi earned a win yet disappointing start to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a competitive ten-round fight at the Manchester venue.
But the challenger had his moments, delivering effective single shots in a match where the approaches never quite clicked, with excessive holding marring the fight.
The officials had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi said in the arena as he was met by disapproval from the spectators.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to earn a 20th pro success.
Various analysts felt the challenger, thirty-one, deserved the decision but the contender experienced the second setback of his 28-match career.
The Champion Claims Victory in Uneventful Encounter
His career development has stalled in recent years through contract problems and extended periods of lack of fights.
Earlier forecast as the future of UK boxing, he now is positioned trying to realize his potential - perhaps in what seems like a ultimate opportunity - under recent support.
He began cautiously, with both competitors prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after damaging his hand in the contest, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to narrowly win the better stanzas.
The audience's tolerance decreased because of constant clinching, with the challenger falling to the floor multiple occasions during grappling.
The underdog closed well, but many rounds were challenging to assess. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Fight
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a excellent local rivalry battle to win the continental championship.
The stadium grew hushed for a profoundly moving homage before the fight as 10 bells rang in honor of Manchester's own Hatton, who died aged 46 in last month.
It was the premier televised match card in the city since the passing of Hatton. As the last bell ended, the silence became a roar of "there's only one Ricky Hatton".
The action inside the ropes equaled the feeling. Arthur was floored by a left hook directly to the face in the early round, rising shakily to his footing on the count of eight.
But the traditional red attire of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was injured early, heavy swelling forming under his face as the fighters landed powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur narrowly won the result with scoring tallies of 114-114, narrow lead and 115-112, but each competitor were persistent and full of heart, all the qualities their inspiration the legend stood for.
