UK light-heavyweight Joshua Buatsi earned a win yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a tight ten-round contest at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful clean blows in a contest where the approaches never quite clicked, with constant grabbing spoiling the fight.
The officials had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They win," Buatsi stated in the arena as he was greeted with disapproval from the spectators.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a 20th career victory.
Some ringside observers felt the challenger, 31, deserved the decision but the contender suffered the second loss of his 28-fight professional journey.
The Champion Secures Triumph in Slow Encounter
Buatsi's progress has plateaued in recent years through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of British boxing, he now stands trying to realize his potential - perhaps in what appears to be a last chance - under recent support.
He started carefully, with the two boxers prepared to take risks in a cagey opening few rounds.
Parker, whose only previous defeat came at super middleweight 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 halfway stage, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to narrowly win the better periods.
The spectators' acceptance diminished amid frequent holding, with Parker falling to the floor multiple occasions during grappling.
The underdog ended stronger, but several stanzas were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Russian star Bivol ruling the division, the journey to titles - based on this performance - still appears challenging.
Hatton Memorial Motivates Local Rivalry Battle
In the supporting bout, Arthur beat Rea by split-decision in a excellent local rivalry contest to capture the European light heavyweight title.
The venue fell silent for a extremely emotional tribute ahead of the contest as ten bells tolled in remembrance of the city's native Hatton, who died aged 46 in last month.
It was the initial significant broadcast match card in the city since Hatton's death. As the last bell disappeared, the quiet gave way to a shout of "only one Ricky Hatton".
The action inside the ropes reflected the emotion. The eventual winner was knocked down by a left hook squarely on the chin in the second round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged quickly, noticeable damage developing under his face as the fighters landed powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur barely secured the verdict with scoring tallies of draw, close margin and clearer margin, but both fighters were relentless and full of heart, exactly what their idol Hatton embodied.
