British light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a close ten-round bout at the Manchester venue.
But Parker found success, connecting with powerful single shots in a contest where the techniques didn't complement each other, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but what do champions do? They win," the victor said in the ringside as he was greeted with negative reactions from the crowd.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in February - to secure a 20th career victory.
Several boxing experts felt the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter suffered the second loss of his 28-fight professional journey.
Buatsi Earns Triumph in Uneventful Match
The fighter's advancement has stalled in recent times through contract problems and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with the two boxers ready to be aggressive in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was participating in his second bout at light-heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to barely take the more effective stanzas.
The crowd's patience decreased amid frequent holding, with Parker going down multiple occasions during clinches.
The underdog closed well, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian star Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Inspires All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a terrific Manchester vs Manchester contest to win the European light heavyweight championship.
The venue became quiet for a profoundly moving homage before the fight as a bell ceremony sounded in memory of the city's native Ricky Hatton, who passed away at age 46 in last month.
It was the first major televised fight night in the urban center since Hatton's passing. As the concluding sound ended, the stillness gave way to a shout of "there's only one Ricky Hatton".
The action during the bout equaled the emotion. Arthur was floored by a powerful punch squarely on the jaw in the second round, standing uncertainly to his position on the count of eight.
But the Manchester United-red equipment of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was injured early, noticeable damage appearing under his face as the fighters landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the action rarely dropped over the full distance.
Arthur narrowly won the verdict with judges scorecards of even score, close margin and clearer margin, but each competitor were persistent and full of heart, all the qualities their hero the legend stood for.
