British light heavyweight Joshua Buatsi secured a victory yet unimpressive start to his career under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker had his moments, landing some telling single shots in a fight where the approaches didn't complement each other, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 to the winner, with the third a 95-95.
"It wasn't my finest performance but what do champions do? They prevail," the victor stated in the arena as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to earn a 20th pro success.
Some ringside observers thought Parker, thirty-one, deserved the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
Buatsi Secures Triumph in Dull Encounter
Buatsi's progress has plateaued in the past few years through management issues and extended periods of inactivity.
Once tipped as the rising talent of the British fight scene, he now stands trying to realize his potential - maybe in what seems like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers willing to take risks in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was making just his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who operated with a protective stance to barely take the cleaner periods.
The audience's tolerance diminished during frequent holding, with the challenger slipping to the canvas several times during grappling.
Parker closed well, but multiple periods were difficult to score. Nevertheless, ex-champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Homage Fuels Local Rivalry Fight
In the supporting bout, Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester battle to win the continental belt.
The stadium grew hushed for a deeply poignant homage before the fight as a bell ceremony sounded in memory of the city's native Ricky Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the city since Hatton's death. As the final chime ended, the quiet gave way to a roar of "there's only one Hatton".
The action during the bout matched the sentiment. The eventual winner was sent to the canvas by a left hook squarely on the jaw in the early round, rising shakily 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 competitive blue - was marked up early, significant bruising forming under his orbital area as the duo landed powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur edged the result with scoring tallies of draw, narrow lead and 115-112, but each competitor were relentless and courageous, exactly what their idol Hatton represented.
