British light heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker found success, connecting with powerful single shots in a fight where the techniques failed to mesh, with excessive holding marring the action.
Two judges had it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my greatest performance but what do champions do? They prevail," the victor commented in the ringside as he was greeted with boos from the audience.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts thought the challenger, thirty-one, merited the decision but the British boxer experienced the second setback of his 28-fight professional journey.
Buatsi Earns Victory in Dull Encounter
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a last chance - under new promotional backing.
He began cautiously, with both competitors ready to overcommit in a calculated initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to barely take the better rounds.
The audience's tolerance diminished amid regular grabbing, with the challenger going down various instances during clinches.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Memorial Motivates All-Manchester Fight
In the secondary fight, Arthur beat Bradley Rea by close verdict in a excellent all-Manchester contest to secure the continental title.
The arena grew hushed for a extremely emotional tribute ahead of the contest as 10 bells tolled in memory of the city's native Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast match card in the city since Hatton's passing. As the final chime disappeared, the stillness transitioned to a roar of "there's just one Ricky Hatton".
The fighting within the ring equaled the emotion. Arthur was sent to the canvas by a significant blow flush on the face in the early round, getting up unsteadily to his feet on the count of eight.
But the red-colored attire of the fighter soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged soon, noticeable damage developing under his face as the pair traded hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over the full distance.
Arthur barely secured the verdict with judges scorecards of draw, narrow lead and clearer margin, but each competitor were relentless and courageous, all the qualities their idol Hatton represented.
