British light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a majority decision in a competitive 10-round contest at the boxing arena.
But Parker found success, connecting with powerful single shots in a contest where the approaches failed to mesh, with frequent clinching spoiling the fight.
Two judges had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best showing but what defines champions? They prevail," the victor said in the ring as he was faced negative reactions from the spectators.
The British fighter returned to winning ways after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the decision but the contender endured the second setback of his 28-fight professional journey.
The Champion Claims Win in Uneventful Encounter
His career development has plateaued in recent years through management issues and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to fulfil that early promise - maybe in what seems like a last chance - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a calculated initial rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for the favorite, who operated with a protective stance to edge the cleaner rounds.
The audience's tolerance wore thin because of constant clinching, with Parker slipping to the canvas several times during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just one round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Hatton Tribute Inspires Local Rivalry Contest
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding all-Manchester battle to win the continental belt.
The arena grew hushed for a extremely emotional memorial prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the last bell ended, the stillness transitioned to a shout of "there's only one Ricky Hatton".
The action during the bout equaled the feeling. The eventual winner was floored by a powerful punch squarely on the face in the initial stage, getting up unsteadily to his footing on the eight count.
But the red-colored shorts of Arthur soon advanced again. Across the ring, the opponent - in competitive blue - was marked up soon, noticeable damage appearing under his eye as the pair landed hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the action hardly diminished over the full distance.
The victor barely secured the result with scoring tallies of even score, close margin and wider gap, but each competitor were persistent and brave, everything their hero the legend represented.
