UK light heavyweight Joshua Buatsi earned a win yet disappointing debut to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective single shots in a match where the approaches didn't complement each other, with constant grabbing marring the fight.
The officials had it 96-94 for to the winner, with the third a even score.
"It wasn't my finest performance but how do champions respond? They succeed," the victor stated in the ring as he was faced disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts believed Parker, thirty-one, merited the decision but the contender suffered the second setback of his 28-bout career.
The Champion Earns Triumph in Slow Affair
His career development has plateaued in the past few years through promotional disputes and extended periods of lack of fights.
Previously predicted as the next star of the British fight scene, he now finds himself trying to achieve expectations - possibly in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter ready to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second fight at light heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for Buatsi, who utilized a protective stance to edge the more effective periods.
The crowd's patience wore thin during constant clinching, with Parker going down various instances during grappling.
The underdog ended stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Motivates Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific local rivalry fight to secure the European light-heavyweight belt.
The venue fell silent for a profoundly moving tribute ahead of the contest as a bell ceremony sounded in remembrance of the city's native Hatton, who passed away aged 46 in last month.
It was the first major televised boxing event in the city since Hatton's death. As the concluding sound disappeared, the silence gave way to a chant of "there's only one Ricky Hatton".
The competition inside the ropes matched the sentiment. Arthur was floored by a significant blow directly to the jaw in the early round, getting up unsteadily to his footing on the referee's count.
But the red-colored equipment of Arthur soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up early, significant bruising appearing under his orbital area as the pair landed hard punches.
The challenger, 27, connected with strong blows but the champion, 34, responded in kind with stinging uppercuts as the pace seldom decreased over twelve rounds.
The victor edged the decision with judges scorecards of draw, narrow lead and clearer margin, but both fighters were determined and full of heart, exactly what their inspiration Hatton stood for.
