UK light-heavyweight Joshua Buatsi made a winning yet unimpressive debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a competitive 10-round bout at the Manchester venue.
But the challenger had his moments, delivering effective individual punches in a match where the styles never quite clicked, with constant grabbing spoiling the contest.
The scoring judges had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my greatest performance but what defines champions? They win," Buatsi commented in the ring as he was faced negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a twentieth professional win.
Various analysts believed the challenger, 31, deserved the victory but the Derbyshire fighter experienced the second defeat of his 28-fight professional journey.
The Champion Earns Victory in Dull Affair
His career development has stalled in recent years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter willing to take risks in a tentative initial rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who utilized a protective stance to barely take the more effective stanzas.
The spectators' acceptance diminished during regular grabbing, with the challenger slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were hard to judge. However, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a outstanding Manchester vs Manchester fight to win the European light-heavyweight belt.
The arena fell silent for a extremely emotional tribute before the fight as ten bells tolled in remembrance of local hero Hatton, who passed away at age 46 in September.
It was the first major televised boxing event in the city since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a roar of "there's only one Hatton".
The fighting during the bout equaled the emotion. The eventual winner was sent to the canvas by a significant blow directly to the chin in the early round, rising shakily to his footing on the count of eight.
But the traditional red equipment of Arthur soon advanced again. Across the ring, the opponent - in opposing blue - was marked up soon, significant bruising forming under his face as the duo traded hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor edged the decision with scoring tallies of even score, close margin and wider gap, but both fighters were determined and courageous, all the qualities their inspiration the legend embodied.
