UK light heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive 10-round bout at the Manchester venue.
But the challenger had his moments, delivering effective single shots in a match where the styles didn't complement each other, with excessive holding disrupting the fight.
Two judges had it 96-94 for to the winner, with the third a 95-95.
"It wasn't my greatest performance but how do champions respond? They succeed," Buatsi said in the ringside as he was faced disapproval from the audience.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th career victory.
Some ringside observers thought Parker, 31, deserved the victory but the Derbyshire fighter endured the second loss of his 28-fight career.
Buatsi Secures Victory in Dull Encounter
His career development has stalled in the past few years through contract problems and extended periods of inactivity.
Once tipped as the next star of the British fight scene, he now stands trying to achieve expectations - possibly in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with the two boxers ready to take risks in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second fight at light heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for Buatsi, who operated with a protective stance to barely take the more effective stanzas.
The crowd's patience decreased amid regular grabbing, with the challenger slipping to the canvas several times during grappling.
The underdog closed well, but multiple periods were hard to judge. However, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the likes of heavy hitter David Benavidez, and Russian champion Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Hatton Homage Fuels Manchester Derby Contest
In the secondary fight, Lyndon Arthur defeated Rea by close verdict in a terrific all-Manchester fight to secure the continental belt.
The arena fell silent for a deeply poignant homage prior to the bout as 10 bells tolled in memory of local hero Hatton, who succumbed 46 years old in last month.
It was the first major televised match card in the location since Hatton's death. As the concluding sound ended, the stillness gave way to a chant of "only one Ricky Hatton".
The competition within the ring matched the feeling. The eventual winner was sent to the canvas by a significant blow squarely on the chin in the initial stage, rising shakily to his footing on the count of eight.
But the traditional red equipment of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was marked up quickly, noticeable damage appearing under his face as the duo traded powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over the full distance.
The victor narrowly won the result with official scores of draw, 115-113 and 115-112, but each competitor were relentless and full of heart, exactly what their idol the legend embodied.
