British light-heavyweight Joshua Buatsi secured a victory yet disappointing debut to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a close ten-round bout at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a match where the styles never quite clicked, with constant grabbing marring the contest.
The scoring judges judged it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They prevail," the victor said in the arena as he was faced boos from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, merited the win but the British boxer experienced the second defeat of his 28-match career.
The Champion Earns Victory in Slow Encounter
His career development has stalled in recent years through management issues and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now finds himself trying to realize his potential - perhaps in what seems like a ultimate opportunity - under fresh management.
He started carefully, with both competitors willing to be aggressive in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for Buatsi, who operated with a protective stance to narrowly win the cleaner rounds.
The audience's tolerance decreased during regular grabbing, with the challenger falling to the floor several times during clinches.
The underdog closed well, but multiple periods were challenging to assess. Although, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Tribute Inspires Local Rivalry Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester battle to win the European light-heavyweight title.
The stadium grew hushed for a extremely emotional tribute before the fight as a bell ceremony rang in remembrance of Manchester's own Hatton, who died at age 46 in September.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the last bell ended, the stillness transitioned to a roar of "there's just one Ricky Hatton".
The action inside the ropes matched the emotion. Arthur was knocked down by a left hook flush on the jaw in the early round, rising shakily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was injured quickly, noticeable damage appearing under his eye as the fighters exchanged powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over the full distance.
Arthur barely secured the result with scoring tallies of 114-114, close margin and 115-112, but each competitor were persistent and full of heart, everything their inspiration the legend represented.
