UK light-heavyweight Joshua Buatsi made a winning yet disappointing debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a competitive ten-round contest at the Manchester venue.
But Parker had his moments, delivering effective single shots in a match where the styles never quite clicked, with constant grabbing disrupting the fight.
Two judges had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best showing but how do champions respond? They succeed," Buatsi said in the arena as he was greeted with disapproval from the spectators.
The British fighter returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Some ringside observers felt Parker, thirty-one, merited the decision but the Derbyshire fighter experienced the second loss of his 28-fight professional journey.
Buatsi Secures Victory in Uneventful Match
Buatsi's progress has slowed in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the rising talent of British boxing, he now finds himself trying to fulfil that early promise - perhaps in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with both competitors ready to take risks in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who operated with a solid defense to barely take the more effective rounds.
The audience's tolerance diminished amid frequent holding, with Parker slipping to the canvas various instances during clinches.
Parker closed well, but multiple periods were hard to judge. However, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor progresses, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Contest
In the co-main event, Arthur defeated Rea by divided decision in a outstanding all-Manchester fight to win the European light-heavyweight championship.
The arena fell silent for a extremely emotional homage ahead of the contest as a bell ceremony tolled in remembrance of Manchester's own Hatton, who succumbed at age 46 in September.
It was the premier televised fight night in the location since Hatton's death. As the last bell disappeared, the silence gave way to a chant of "there's only one Ricky Hatton".
The competition inside the ropes reflected the feeling. The eventual winner was floored by a significant blow directly to the chin in the early round, standing uncertainly to his footing on the eight count.
But the red-colored shorts of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was damaged soon, significant bruising appearing under his orbital area as the duo traded powerful shots.
Rea, 27, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur barely secured the decision with official scores of 114-114, narrow lead and 115-112, but the two athletes were relentless and full of heart, exactly what their idol the legend embodied.
