UK light-heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive ten-round bout at the Manchester venue.
But the challenger had his moments, delivering effective clean blows in a match where the approaches never quite clicked, with excessive holding marring the action.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi said in the ringside as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to earn a twentieth professional win.
Various analysts felt the challenger, thirty-one, merited the victory but the contender endured the second loss of his 28-bout career.
Buatsi Secures Victory in Slow Match
The fighter's advancement has slowed in the past few years through management issues and long spells of lack of fights.
Earlier forecast as the rising talent of British boxing, he now stands trying to realize his potential - possibly in what appears to be a final roll of the dice - under recent support.
He started carefully, with the two boxers prepared to be aggressive in a calculated initial rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who worked behind a solid defense to narrowly win the more effective periods.
The audience's tolerance wore thin amid constant clinching, with Parker slipping to the canvas various instances during close exchanges.
The underdog ended stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a outstanding Manchester vs Manchester contest to win the European light heavyweight championship.
The stadium grew hushed for a extremely emotional tribute before the fight as ten bells rang in remembrance of the city's native Hatton, who died aged 46 in recently.
It was the first major televised match card in the urban center since Hatton's death. As the concluding sound disappeared, the quiet transitioned to a chant of "only one Ricky Hatton".
The fighting within the ring reflected the feeling. Arthur was knocked down by a left hook flush on the chin in the early round, standing uncertainly to his footing on the eight count.
But the traditional red attire of the fighter soon advanced again. On the opposite side, the opponent - in opposing blue - was marked up soon, noticeable damage appearing under his orbital area as the pair exchanged hard punches.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over twelve rounds.
Arthur narrowly won the verdict with scoring tallies of even score, 115-113 and 115-112, but the two athletes were relentless and brave, exactly what their hero the legend embodied.
