UK light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight 10-round bout at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a fight where the styles never quite clicked, with constant grabbing spoiling the fight.
Two judges scored it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my best display but how do champions respond? They succeed," Buatsi stated in the arena as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an thrilling contest with his previous opponent in last winter - to secure a 20th pro success.
Various analysts thought the challenger, thirty-one, merited the decision but the contender suffered the second defeat of his 28-bout career.
The Champion Secures Win in Dull Match
Buatsi's progress has plateaued in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the next star of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers willing to overcommit in a cagey initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was making just his second fight at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who utilized a tight guard to barely take the more effective stanzas.
The audience's tolerance wore thin during frequent holding, with Parker falling to the floor various instances during close exchanges.
The underdog closed well, but several stanzas were difficult to score. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Hatton Memorial Inspires Manchester Derby Battle
In the co-main event, Arthur beat Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the continental belt.
The stadium fell silent for a deeply poignant homage before the fight as a bell ceremony tolled in honor of local hero Ricky Hatton, who died aged 46 in last month.
It was the premier televised boxing event in the city since the passing of Hatton. As the final chime faded, the stillness became a chant of "there's only one Hatton".
The competition within the ring equaled the emotion. Arthur was sent to the canvas by a left hook flush on the jaw in the second round, rising shakily to his footing on the referee's count.
But the red-colored equipment of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was injured early, significant bruising developing under his face as the fighters traded punishing blows.
The challenger, 27, landed power punches but the champion, thirty-four, fought fire with fire with stinging uppercuts as the intensity seldom decreased over 12 rounds.
Arthur edged the result with judges scorecards of 114-114, close margin and 115-112, but each competitor were persistent and courageous, all the qualities their hero Hatton represented.
