British 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 activity level likely gained him a majority decision in a tight ten-round bout at the boxing arena.
But the challenger landed significant shots, landing some telling individual punches in a fight where the styles didn't complement each other, with excessive holding spoiling the action.
The officials judged it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They succeed," Buatsi stated in the ringside as he was greeted with disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Several boxing experts thought the challenger, thirty-one, deserved the decision but the contender endured the second setback of his 28-match professional journey.
The Champion Claims Triumph in Dull Affair
His career development has slowed in recent times through contract problems and extended periods of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to fulfil that early promise - maybe in what appears to be a last chance - under fresh management.
He began cautiously, with both competitors ready to overcommit in a cagey early stages.
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 participating in his second bout at light-heavyweight.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who operated with a tight guard to barely take the better stanzas.
The crowd's patience diminished amid frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Bivol leading the category, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Arthur beat Rea by split-decision in a excellent Manchester vs Manchester battle to secure the European light heavyweight championship.
The venue grew hushed for a extremely emotional homage ahead of the contest as 10 bells tolled in honor of the city's native Hatton, who passed away at age 46 in last month.
It was the first major televised fight night in the location since Hatton's death. As the concluding sound faded, the silence became a roar of "there's only one Hatton".
The action inside the ropes equaled the emotion. The eventual winner was floored by a left hook squarely on the face in the early round, rising shakily to his position on the count of eight.
But the red-colored attire of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was marked up early, heavy swelling forming under his face as the fighters landed hard punches.
The challenger, 27, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the action hardly diminished over twelve rounds.
The victor edged the result with judges scorecards of draw, narrow lead and 115-112, but the two athletes were persistent and courageous, exactly what their hero Hatton represented.
