British light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a close ten-round fight at the Manchester venue.
But the challenger landed significant shots, delivering effective single shots in a match where the approaches didn't complement each other, with excessive holding spoiling the fight.
The officials had it 96-94 for to the winner, with the third a 95-95.
"It wasn't my greatest performance but what defines champions? They win," Buatsi said in the ring as he was met by disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Various analysts felt Parker, 31, merited the win but the Derbyshire fighter endured the second setback of his 28-match professional journey.
Buatsi Claims Triumph in Slow Affair
The fighter's advancement has stalled in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter prepared to take risks in a cagey initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for Buatsi, who utilized a protective stance to edge the more effective periods.
The audience's tolerance diminished because of constant clinching, with the challenger slipping to the canvas various instances during clinches.
The underdog closed well, but multiple periods were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - judging by this showing - still looks steep.
Hatton Tribute Fuels Local Rivalry Fight
In the co-main event, Lyndon Arthur defeated Rea by divided decision in a terrific Manchester vs Manchester fight to secure the continental belt.
The arena became quiet for a deeply poignant tribute prior to the bout as a bell ceremony rang in remembrance of local hero Ricky Hatton, who succumbed aged 46 in last month.
It was the first major televised match card in the urban center since Hatton's death. As the last bell faded, the stillness became a roar of "there's only one Ricky Hatton".
The fighting during the bout matched the emotion. Arthur was knocked down by a powerful punch squarely on the chin in the initial stage, standing uncertainly to his footing on the referee's count.
But the traditional red attire of Arthur soon came forward again. From the other corner, the opponent - in rival City blue - was damaged soon, significant bruising appearing under his orbital area as the fighters traded punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the result with judges scorecards of draw, 115-113 and wider gap, but the two athletes were relentless and brave, all the qualities their inspiration Hatton embodied.
