British light-heavyweight Joshua Buatsi secured a victory yet disappointing start to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a close ten-round contest at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful individual punches in a match where the approaches failed to mesh, with frequent clinching marring the contest.
The officials had it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my best display but how do champions respond? They prevail," Buatsi stated in the ring as he was met by disapproval from the audience.
The British fighter got back to winning after his initial pro loss - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Some ringside observers believed the challenger, 31, should have been awarded the decision but the British boxer suffered the second loss of his 28-fight professional journey.
The Champion Claims Victory in Uneventful Affair
Buatsi's progress has slowed in recent times through contract problems and extended periods of lack of fights.
Once tipped as the future of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what appears to be a last chance - under recent support.
He opened tentatively, with both competitors prepared to be aggressive in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second fight at light-heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who worked behind a tight guard to barely take the cleaner periods.
The spectators' acceptance decreased because of constant clinching, with the challenger slipping to the canvas several times during grappling.
The underdog finished the stronger, but multiple periods were hard to judge. Although, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Memorial Fuels All-Manchester Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent all-Manchester contest to capture the European light-heavyweight belt.
The stadium grew hushed for a extremely emotional tribute before the fight as ten bells sounded in remembrance of Manchester's own Ricky Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a chant of "only one Ricky Hatton".
The fighting during the bout matched the sentiment. Arthur was sent to the canvas by a powerful punch directly to the chin in the initial stage, standing uncertainly to his feet on the referee's count.
But the Manchester United-red equipment of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was damaged quickly, heavy swelling forming under his face as the pair landed powerful shots.
Rea, 27, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the pace hardly diminished over 12 rounds.
The victor edged the result with official scores of draw, narrow lead and clearer margin, but both fighters were relentless and courageous, exactly what their hero the legend stood for.
