UK light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a close ten-round contest at the Co-op Live Arena.
But the challenger found success, landing some telling single shots in a match where the techniques didn't complement each other, with excessive holding spoiling the fight.
The officials judged it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best performance but what defines champions? They prevail," the victor stated in the ringside as he was faced negative reactions from the audience.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to claim a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the British boxer endured the second setback of his 28-fight professional journey.
The Champion Claims Triumph in Uneventful Match
His career development has slowed in the past few years through management issues and considerable time of inactivity.
Previously predicted as the next star of the British fight scene, he now finds himself trying to achieve expectations - possibly in what appears to be a last chance - under fresh management.
He began cautiously, with the two boxers ready to overcommit in a calculated initial rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second fight at light heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who utilized a tight guard to edge the cleaner periods.
The spectators' acceptance wore thin because of regular grabbing, with Parker falling to the floor several times during grappling.
The underdog closed well, but several stanzas were difficult to score. Nevertheless, former world champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just one round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Hatton Tribute Fuels Local Rivalry Contest
In the secondary fight, Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester battle to capture the continental championship.
The venue grew hushed for a deeply poignant homage prior to the bout as 10 bells sounded in honor of Manchester's own Ricky Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast fight night in the location since Hatton's death. As the last bell faded, the stillness became a shout of "there's just one Ricky Hatton".
The fighting during the bout matched the sentiment. Arthur was knocked down by a powerful punch directly to the jaw in the initial stage, standing uncertainly to his position on the referee's count.
But the traditional red equipment of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was damaged early, significant bruising developing under his face as the pair exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
The victor narrowly won the verdict with official scores of draw, narrow lead and clearer margin, but the two athletes were determined and brave, all the qualities their idol Hatton represented.
