UK light heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a competitive 10-round bout at the boxing arena.
But the challenger had his moments, connecting with powerful individual punches in a fight where the styles failed to mesh, with excessive holding disrupting the fight.
The officials scored it 96-94 in favor to the winner, with the third a even score.
"It wasn't my greatest display but what do champions do? They prevail," the victor commented in the arena as he was greeted with negative reactions from the spectators.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th pro success.
Various analysts believed the challenger, 31, deserved the win but the contender endured the second loss of his 28-match career.
Buatsi Claims Triumph in Uneventful Encounter
His career development has stalled in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was competing in only his second fight at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to edge the better periods.
The spectators' acceptance decreased during frequent holding, with Parker going down several times during clinches.
Parker closed well, but multiple periods were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Russian star Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Arthur overcame Bradley Rea by close verdict in a terrific local rivalry battle to secure the European light-heavyweight belt.
The venue became quiet for a profoundly moving memorial ahead of the contest as ten bells tolled in honor of the city's native Hatton, who succumbed aged 46 in September.
It was the premier televised match card in the location since Hatton's passing. As the concluding sound faded, the quiet gave way to a roar of "only one Hatton".
The fighting during the bout matched the emotion. Arthur was knocked down by a significant blow directly to the jaw in the early round, standing uncertainly to his position on the eight count.
But the red-colored attire of the fighter soon advanced again. On the opposite side, the opponent - in opposing blue - was injured early, noticeable damage developing under his orbital area as the pair exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the action hardly diminished over 12 rounds.
The victor barely secured the verdict with official scores of 114-114, close margin and clearer margin, but both fighters were determined and courageous, everything their idol Hatton stood for.
