British light heavyweight Joshua Buatsi secured a victory yet unimpressive start to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the approaches didn't complement each other, with excessive holding marring the action.
The officials judged it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest performance but what do champions do? They win," the victor stated in the ringside as he was faced boos from the audience.
The British fighter bounced back after his first professional defeat - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, merited the decision but the Derbyshire fighter endured the second setback of his 28-fight career.
Buatsi Secures Win in Dull Affair
The fighter's advancement has slowed in recent times through contract problems and considerable time of lack of fights.
Previously predicted as the future of British boxing, he now finds himself trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with the two boxers willing to be aggressive in a calculated early stages.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second fight at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who utilized a protective stance to narrowly win the better periods.
The spectators' acceptance decreased during constant clinching, with the challenger going down various instances during close exchanges.
Parker closed well, but many rounds were difficult to score. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi advances, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Battle
In the supporting bout, Lyndon Arthur beat Rea by close verdict in a terrific Manchester vs Manchester contest to win the European light heavyweight belt.
The arena fell silent for a profoundly moving tribute ahead of the contest as a bell ceremony tolled in memory of the city's native Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised boxing event in the urban center since Hatton's passing. As the concluding sound faded, the silence became a roar of "only one Hatton".
The action during the bout reflected the emotion. Arthur was floored by a significant blow directly to the chin in the second round, standing uncertainly to his footing on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was injured early, significant bruising developing under his eye as the fighters traded powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over twelve rounds.
The victor narrowly won the decision with scoring tallies of 114-114, 115-113 and 115-112, but both fighters were persistent and full of heart, all the qualities their hero Hatton embodied.
