British light-heavyweight Joshua Buatsi made a winning yet disappointing beginning to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a match where the techniques never quite clicked, with frequent clinching spoiling the action.
Two judges judged it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They prevail," the victor said in the ringside as he was faced boos from the crowd.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in February - to secure a 20th career victory.
Some ringside observers believed the challenger, thirty-one, deserved the decision but the Derbyshire fighter experienced the second setback of his 28-match career.
The Champion Secures Victory in Slow Affair
Buatsi's progress has stalled in the past few years through contract problems and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter prepared to overcommit in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who utilized a solid defense to narrowly win the better stanzas.
The spectators' acceptance diminished during constant clinching, with Parker going down multiple occasions during grappling.
The underdog ended stronger, but multiple periods were challenging to assess. Although, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the caliber of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Motivates All-Manchester Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific local rivalry battle to win the European light heavyweight belt.
The venue grew hushed for a profoundly moving tribute prior to the bout as ten bells rang in memory of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the final chime disappeared, the quiet gave way to a shout of "there's just one Hatton".
The action during the bout reflected the feeling. Arthur was sent to the canvas by a significant blow squarely on the face in the early round, rising shakily to his footing on the eight count.
But the red-colored attire of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was marked up soon, significant bruising appearing under his eye as the duo landed powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
The victor barely secured the decision with scoring tallies of draw, close margin and 115-112, but both fighters were determined and brave, exactly what their idol Hatton embodied.
