UK light-heavyweight Joshua Buatsi earned a win yet underwhelming debut to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive 10-round bout at the Manchester venue.
But the challenger landed significant shots, delivering effective single shots in a contest where the techniques never quite clicked, with excessive holding spoiling the action.
The scoring judges scored it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my best showing but how do champions respond? They succeed," the victor stated in the ringside as he was faced boos from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts felt the challenger, thirty-one, merited the decision but the Derbyshire fighter experienced the second loss of his 28-fight professional journey.
Buatsi Earns Triumph in Uneventful Encounter
The fighter's advancement has plateaued in the past few years through promotional disputes and considerable time of lack of fights.
Once tipped as the rising talent of the British fight scene, he now stands trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under recent support.
He started carefully, with both competitors prepared to take risks in a calculated opening few rounds.
Parker, whose only previous defeat came at the lower weight class 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, making life awkward for the favorite, who worked behind a solid defense to narrowly win the cleaner stanzas.
The crowd's patience wore thin during regular grabbing, with the challenger falling to the floor multiple occasions during grappling.
The underdog ended stronger, but multiple periods were challenging to assess. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Memorial Motivates All-Manchester Battle
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a outstanding all-Manchester contest to win the continental belt.
The arena became quiet for a extremely emotional homage before the fight as ten bells sounded in memory of local hero Hatton, who succumbed at age 46 in last month.
It was the premier televised match card in the city since Hatton's death. As the last bell faded, the quiet gave way to a roar of "there's just one Ricky Hatton".
The competition within the ring equaled the sentiment. Arthur was sent to the canvas by a significant blow directly to the face in the second round, standing uncertainly to his position on the referee's count.
But the red-colored equipment of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was damaged quickly, heavy swelling appearing under his eye as the duo exchanged hard punches.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the action seldom decreased over twelve rounds.
Arthur edged the result with scoring tallies of draw, 115-113 and wider gap, but both fighters were persistent and full of heart, all the qualities their inspiration the legend represented.
