British light heavyweight Joshua Buatsi made a winning yet disappointing start to his career under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a competitive ten-round fight at the boxing arena.
But Parker landed significant shots, landing some telling clean blows in a fight where the techniques never quite clicked, with excessive holding spoiling the fight.
The scoring judges scored it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They prevail," Buatsi commented in the ring as he was greeted with negative reactions from the crowd.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, should have been awarded the win but the British boxer suffered the second defeat of his 28-match professional journey.
The Champion Claims Victory in Slow Encounter
Buatsi's progress has slowed in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to achieve expectations - maybe in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter willing to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second bout at the higher weight class.
By the halfway stage, Parker had made it competitive, making life awkward for Buatsi, who operated with a tight guard to barely take the better periods.
The crowd's patience diminished amid frequent holding, with the challenger falling to the floor various instances during grappling.
Parker closed well, but multiple periods were difficult to score. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Tribute Motivates All-Manchester Contest
In the co-main event, Lyndon Arthur beat Rea by split-decision in a excellent Manchester vs Manchester battle to secure the continental title.
The arena became quiet for a profoundly moving homage ahead of the contest as 10 bells sounded in remembrance of local hero Ricky Hatton, who died aged 46 in recently.
It was the first major televised boxing event in the location since Hatton's passing. As the final chime ended, the silence transitioned to a shout of "only one Ricky Hatton".
The action during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. Across the ring, Rea - in rival City blue - was marked up early, significant bruising appearing under his orbital area as the duo traded hard punches.
The challenger, twenty-seven, landed power punches but Arthur, 34, matched the intensity with stinging uppercuts as the action hardly diminished over 12 rounds.
Arthur barely secured the decision with official scores of even score, 115-113 and clearer margin, but each competitor were persistent and full of heart, exactly what their hero the legend represented.
