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 medal winner's activity level appeared to earn him a split decision in a competitive ten-round fight at the Manchester venue.
But the challenger landed significant shots, delivering effective individual punches in a contest where the approaches failed to mesh, with constant grabbing spoiling the fight.
Two judges judged it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my greatest showing but what do champions do? They win," Buatsi said in the ring as he was greeted with negative reactions from the audience.
The British fighter got back to winning after his initial pro loss - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, deserved the victory but the British boxer experienced the second setback of his 28-fight career.
The Champion Earns Victory in Dull Encounter
His career development has plateaued in recent times through management issues and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to take risks in a calculated opening few rounds.
Parker, 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 appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to narrowly win the cleaner periods.
The spectators' acceptance diminished during regular grabbing, with Parker going down multiple occasions during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, former world champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the likes of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Motivates Manchester Derby Fight
In the co-main event, Lyndon Arthur defeated Rea by split-decision in a outstanding local rivalry contest to win the European light-heavyweight championship.
The venue became quiet for a deeply poignant memorial ahead of the contest as a bell ceremony sounded in honor of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the first major televised fight night in the city since Hatton's death. As the concluding sound ended, the silence transitioned to a shout of "there's only one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was floored by a powerful punch squarely on the jaw in the second round, rising shakily to his position on the count of eight.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up quickly, heavy swelling forming under his eye as the fighters landed hard punches.
The challenger, 27, delivered effective strikes but the champion, 34, fought fire with fire with effective uppercuts as the intensity rarely dropped over twelve rounds.
The victor edged the verdict with scoring tallies of even score, narrow lead and wider gap, but the two athletes were persistent and full of heart, exactly what their idol Hatton embodied.
