UK light-heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a competitive ten-round contest at the Manchester venue.
But Parker found success, delivering effective single shots in a match where the techniques didn't complement each other, with excessive holding marring the contest.
The officials judged it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best display but how do champions respond? They prevail," Buatsi said in the arena as he was faced disapproval from the spectators.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Various analysts thought Parker, 31, deserved the win but the British boxer suffered the second defeat of his 28-fight professional journey.
Buatsi Secures Win in Dull Affair
The fighter's advancement has stalled in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to achieve expectations - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter prepared to be aggressive in a cagey opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second appearance at light heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who utilized a protective stance to narrowly win the better periods.
The crowd's patience decreased because of constant clinching, with Parker falling to the floor multiple occasions during clinches.
Parker ended stronger, but many rounds were hard to judge. Although, previous titleholder Carl Frampton - working with the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just one round.
The victor moves on, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - based on this performance - still looks steep.
Hatton Memorial Inspires Local Rivalry Contest
In the secondary fight, Lyndon Arthur defeated Bradley Rea by split-decision in a excellent local rivalry fight to win the European light heavyweight belt.
The stadium fell silent for a profoundly moving tribute before the fight as 10 bells rang in honor of local hero Hatton, who died 46 years old in last month.
It was the premier televised match card in the urban center since Hatton's death. As the last bell faded, the stillness gave way to a chant of "only one Ricky Hatton".
The action during the bout equaled the feeling. Arthur was floored by a significant blow directly to the face in the initial stage, getting up unsteadily to his position on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was marked up soon, noticeable damage appearing under his eye as the duo landed hard punches.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor barely secured the decision with scoring tallies of even score, narrow lead and 115-112, but the two athletes were persistent and brave, exactly what their inspiration the legend stood for.
