British light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career 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 judges' verdict in a tight ten-round bout at the Co-op Live Arena.
But the challenger found success, delivering effective clean blows in a fight where the styles never quite clicked, with constant grabbing spoiling the fight.
The scoring judges had it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but what do champions do? They prevail," the victor said in the arena as he was greeted with disapproval from the crowd.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers believed Parker, 31, merited the victory but the Derbyshire fighter suffered the second loss of his 28-fight career.
Buatsi Claims Win in Slow Match
The fighter's advancement has plateaued in the past few years through promotional disputes and considerable time of lack of fights.
Previously predicted as the future of UK boxing, he now stands trying to realize his potential - possibly in what appears to be a final roll of the dice - under fresh management.
He started carefully, with neither fighter prepared to take risks in a tentative early stages.
The challenger, 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 making just his second fight at light-heavyweight.
By the halfway stage, Parker had kept it close, causing problems for Buatsi, who utilized a protective stance to narrowly win the more effective stanzas.
The spectators' acceptance wore thin during frequent holding, with Parker slipping to the canvas several times during grappling.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor moves on, but with the likes of power puncher Benavidez, and Russian star Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Contest
In the supporting bout, Lyndon Arthur overcame Rea by divided decision in a outstanding Manchester vs Manchester battle to win the European light heavyweight title.
The venue grew hushed for a profoundly moving homage prior to the bout as ten bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away aged 46 in September.
It was the premier televised boxing event in the location since Hatton's death. As the concluding sound faded, the stillness transitioned to a roar of "there's only one Hatton".
The fighting inside the ropes matched the emotion. The eventual winner was sent to the canvas by a significant blow directly to the face in the initial stage, rising shakily to his feet on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged soon, noticeable damage developing under his orbital area as the fighters landed hard punches.
Rea, 27, landed power punches but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur edged the result with scoring tallies of even score, narrow lead and 115-112, but the two athletes were determined and courageous, everything their hero Hatton represented.
