UK light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a tight 10-round fight at the boxing arena.
But Parker had his moments, delivering effective clean blows in a contest where the approaches failed to mesh, with frequent clinching disrupting the action.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best display but what do champions do? They succeed," Buatsi stated in the ringside as he was met by disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter suffered the second loss of his 28-bout career.
Buatsi Claims Win in Dull Affair
His career development has stalled in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to be aggressive in a cagey early stages.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second appearance at light heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who operated with a solid defense to barely take the better periods.
The spectators' acceptance diminished because of frequent holding, with Parker falling to the floor multiple occasions during grappling.
The underdog finished the stronger, but several stanzas were difficult to score. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor moves on, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Memorial Motivates Manchester Derby Fight
In the co-main event, Arthur defeated Rea by close verdict in a excellent Manchester vs Manchester fight to win the European light-heavyweight title.
The stadium became quiet for a profoundly moving homage prior to the bout as ten bells rang in remembrance of Manchester's own Ricky Hatton, who passed away at age 46 in recently.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime disappeared, the quiet gave way to a chant of "there's just one Hatton".
The competition within the ring reflected the sentiment. Arthur was knocked down by a significant blow directly to the face in the early round, standing uncertainly to his footing on the referee's count.
But the red-colored equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured early, noticeable damage forming under his face as the pair landed hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the action hardly diminished over the full distance.
The victor edged the verdict with scoring tallies of draw, close margin and 115-112, but each competitor were persistent and brave, all the qualities their inspiration Hatton embodied.
