UK light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a competitive 10-round fight at the boxing arena.
But the challenger found success, connecting with powerful clean blows in a match where the techniques didn't complement each other, with frequent clinching marring the fight.
The officials scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what do champions do? They succeed," the victor commented in the ringside as he was greeted with negative reactions from the audience.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, merited the victory but the British boxer endured the second loss of his 28-fight professional journey.
The Champion Secures Victory in Dull Affair
Buatsi's progress has slowed in recent years through contract problems and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with both competitors ready to overcommit in a tentative initial rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second bout at light heavyweight.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who utilized a protective stance to barely take the cleaner rounds.
The crowd's patience wore thin because of frequent holding, with Parker slipping to the canvas various instances during clinches.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, previous titleholder the boxing analyst - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Motivates Manchester Derby Fight
In the supporting bout, Lyndon Arthur beat Rea by close verdict in a outstanding all-Manchester fight to win the European light heavyweight title.
The arena fell silent for a profoundly moving tribute before the fight as ten bells sounded in remembrance of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the first major televised fight night in the urban center since Hatton's death. As the last bell faded, the stillness became a roar of "there's only one Ricky Hatton".
The fighting within the ring equaled the sentiment. The eventual winner was floored by a left hook directly to the jaw in the initial stage, rising shakily to his position on the count of eight.
But the Manchester United-red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was marked up quickly, noticeable damage forming under his orbital area as the duo exchanged powerful shots.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur narrowly won the verdict with judges scorecards of 114-114, close margin and wider gap, but the two athletes were persistent and brave, exactly what their inspiration the legend stood for.
