British light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a judges' verdict in a tight 10-round fight at the Manchester venue.
But Parker found success, delivering effective individual punches in a fight where the styles didn't complement each other, with constant grabbing disrupting the action.
The officials judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi stated in the ringside as he was met by boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, deserved the win but the contender experienced the second loss of his 28-fight career.
Buatsi Secures Win in Slow Encounter
Buatsi's progress has stalled in the past few years through promotional disputes and extended periods of lack of fights.
Once tipped as the future of British boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to overcommit in a tentative initial rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was making just his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, making life awkward for Buatsi, who utilized a protective stance to barely take the better periods.
The audience's tolerance diminished because of frequent holding, with the challenger falling to the floor various instances during grappling.
Parker finished the stronger, but many rounds were hard to judge. However, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
The victor advances, but with the likes of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Manchester Derby Battle
In the supporting bout, Lyndon Arthur defeated Bradley Rea by divided decision in a terrific all-Manchester battle to capture the European light-heavyweight title.
The arena grew hushed for a deeply poignant tribute before the fight as a bell ceremony sounded in memory of Manchester's own Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised fight night in the urban center since Hatton's death. As the final chime faded, the silence became a roar of "there's just one Ricky Hatton".
The competition inside the ropes reflected the feeling. The eventual winner was floored by a powerful punch squarely on the chin in the early round, getting up unsteadily to his footing on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up soon, heavy swelling appearing under his face as the pair traded hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the action seldom decreased over 12 rounds.
The victor edged the decision with official scores of even score, close margin and 115-112, but both fighters were relentless and brave, everything their inspiration Hatton represented.
