UK light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a competitive 10-round fight at the Manchester venue.
But Parker had his moments, landing some telling individual punches in a match where the approaches didn't complement each other, with constant grabbing spoiling the contest.
The officials judged it 96-94 for to the winner, with the third a even score.
"It wasn't my finest display but how do champions respond? They prevail," the victor stated in the arena as he was faced boos from the audience.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts felt the challenger, 31, deserved the victory but the Derbyshire fighter suffered the second defeat of his 28-bout professional journey.
The Champion Secures Triumph in Slow Encounter
His career development has slowed in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of British boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under recent support.
He opened tentatively, with the two boxers willing to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second fight at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a protective stance to narrowly win the more effective periods.
The crowd's patience diminished because of constant clinching, with Parker going down multiple occasions during clinches.
The underdog finished the stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the likes of power puncher Benavidez, and Russian champion Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Homage Motivates Manchester Derby Fight
In the co-main event, Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester battle to win the continental championship.
The venue fell silent for a profoundly moving tribute ahead of the contest as ten bells tolled in honor of the city's native Hatton, who died at age 46 in recently.
It was the first major televised fight night in the urban center since the passing of Hatton. As the final chime ended, the stillness transitioned to a roar of "only one Ricky Hatton".
The fighting during the bout matched the emotion. The eventual winner was floored by a significant blow flush on the jaw in the second round, standing uncertainly to his position on the eight count.
But the Manchester United-red equipment of Arthur soon came forward again. Across the ring, Rea - in competitive blue - was marked up soon, heavy swelling appearing under his eye as the pair traded powerful shots.
Rea, 27, connected with strong blows but Arthur, thirty-four, matched the intensity with powerful upward punches as the action seldom decreased over twelve rounds.
The victor barely secured the result with scoring tallies of draw, 115-113 and clearer margin, but each competitor were determined and brave, everything their inspiration Hatton embodied.
