British light-heavyweight Joshua Buatsi earned a win yet unimpressive start to life 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 majority decision in a close ten-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful individual punches in a contest where the techniques failed to mesh, with excessive holding disrupting the contest.
The officials had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi said in the ring as he was faced disapproval from the crowd.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a 20th career victory.
Some ringside observers felt Parker, 31, merited the decision but the contender endured the second defeat of his 28-match professional journey.
Buatsi Earns Victory in Uneventful Match
His career development has plateaued in the past few years through management issues and considerable time 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 seems like a final roll of the dice - under recent support.
He began cautiously, with neither fighter willing to take risks in a tentative initial rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who worked behind a tight guard to barely take the cleaner stanzas.
The audience's tolerance wore thin because of regular grabbing, with the challenger going down various instances during grappling.
The underdog closed well, but many rounds were hard to judge. Although, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just a single round.
The victor progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Hatton Homage Inspires Manchester Derby Fight
In the secondary fight, Arthur defeated Rea by split-decision in a terrific local rivalry fight to secure the European light-heavyweight belt.
The venue became quiet for a extremely emotional memorial before the fight as 10 bells rang in remembrance of local hero Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the city since the passing of Hatton. As the concluding sound faded, the stillness gave way to a chant of "there's just one Hatton".
The competition during the bout matched the emotion. Arthur was sent to the canvas by a significant blow squarely on the jaw in the second round, getting up unsteadily to his position on the count of eight.
But the traditional red shorts of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was injured early, significant bruising developing under his face as the duo traded powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the intensity hardly diminished over twelve rounds.
The victor barely secured the result with judges scorecards of even score, 115-113 and 115-112, but each competitor were determined and full of heart, everything their inspiration Hatton represented.
