British light-heavyweight Joshua Buatsi earned a win yet underwhelming beginning to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a close 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the techniques didn't complement each other, with frequent clinching spoiling the contest.
Two judges scored it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest showing but what do champions do? They succeed," the victor commented in the ring as he was faced boos from the crowd.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a twentieth professional win.
Some ringside observers believed the challenger, 31, should have been awarded the win but the British boxer endured the second defeat of his 28-fight career.
The Champion Secures Triumph in Slow Match
The fighter's advancement has slowed in recent years through contract problems and long spells of inactivity.
Once tipped as the future of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with both competitors ready to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only his second fight at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the cleaner rounds.
The spectators' acceptance diminished amid constant clinching, with the challenger falling to the floor multiple occasions during clinches.
The underdog finished the stronger, but multiple periods were hard to judge. However, former world champion the boxing analyst - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol leading the category, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry battle to win the continental championship.
The venue grew hushed for a profoundly moving memorial prior to the bout as 10 bells sounded in honor of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the city since Hatton's passing. As the last bell ended, the stillness became a shout of "there's just one Hatton".
The competition inside the ropes matched the sentiment. The eventual winner was knocked down by a powerful punch flush on the chin in the initial stage, getting up unsteadily to his footing on the referee's count.
But the red-colored shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up soon, significant bruising appearing under his eye as the duo traded powerful shots.
Rea, 27, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over the full distance.
The victor barely secured the decision with official scores of even score, 115-113 and clearer margin, but both fighters were determined and brave, exactly what their hero Hatton represented.
