British light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a tight 10-round fight at the boxing arena.
But the challenger had his moments, connecting with powerful clean blows in a match where the approaches didn't complement each other, with constant grabbing disrupting the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They win," the victor stated in the ring as he was greeted with boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to earn a 20th career victory.
Some ringside observers believed Parker, 31, should have been awarded the victory but the Derbyshire fighter endured the second setback of his 28-match professional journey.
The Champion Earns Win in Dull Affair
The fighter's advancement has stalled in the past few years through management issues and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to realize his potential - possibly in what appears to be a last chance - under fresh management.
He started carefully, with neither fighter willing to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand in the contest, was participating in his second fight at light heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who worked behind a tight guard to edge the better rounds.
The crowd's patience diminished amid constant clinching, with the challenger slipping to the canvas various instances during clinches.
Parker finished the stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just one round.
The victor moves on, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Hatton Homage Motivates All-Manchester Battle
In the secondary fight, Arthur beat Rea by split-decision in a excellent local rivalry fight to secure the continental belt.
The stadium fell silent for a deeply poignant homage prior to the bout as a bell ceremony rang in honor of the city's native Hatton, who succumbed at age 46 in recently.
It was the premier televised boxing event in the city since the passing of Hatton. As the concluding sound ended, the stillness transitioned to a shout of "only one Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was knocked down by a powerful punch directly to the face in the early round, getting up unsteadily to his footing on the eight count.
But the traditional red attire of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was injured early, significant bruising forming under his eye as the fighters landed punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the action hardly diminished over 12 rounds.
The victor edged the result with scoring tallies of draw, 115-113 and wider gap, but both fighters were determined and courageous, exactly what their idol Hatton represented.
