UK light heavyweight Joshua Buatsi earned a win yet disappointing start to life under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a competitive 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a fight where the approaches never quite clicked, with constant grabbing marring the contest.
The officials scored it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," the victor commented in the arena as he was faced boos from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to secure a 20th career victory.
Various analysts thought the challenger, thirty-one, merited the win but the British boxer suffered the second setback of his 28-fight professional journey.
The Champion Secures Victory in Dull Match
His career development has plateaued in recent times through promotional disputes and long spells of lack of fights.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to achieve expectations - perhaps in what appears to be a last chance - under new promotional backing.
He began cautiously, with the two boxers prepared to take risks in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second appearance at light-heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for Buatsi, who utilized a protective stance to edge the better rounds.
The audience's tolerance wore thin amid regular grabbing, with Parker going down multiple occasions during grappling.
Parker closed well, but several stanzas were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, giving Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Inspires Local Rivalry Battle
In the supporting bout, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry contest to capture the European light heavyweight title.
The arena fell silent for a profoundly moving tribute prior to the bout as a bell ceremony tolled in honor of local hero Hatton, who passed away at age 46 in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the final chime faded, the silence transitioned to a roar of "there's just one Hatton".
The action during the bout matched the sentiment. Arthur was floored by a significant blow directly to the chin in the early round, getting up unsteadily to his feet on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, Rea - in competitive blue - was injured soon, heavy swelling developing under his orbital area as the duo exchanged hard punches.
The challenger, 27, delivered effective strikes but the champion, 34, fought fire with fire with effective uppercuts as the action rarely dropped over 12 rounds.
The victor edged the decision with judges scorecards of 114-114, narrow lead and wider gap, but both fighters were persistent and brave, exactly what their inspiration Hatton embodied.
