British light heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a judges' verdict in a close 10-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful clean blows in a contest where the approaches never quite clicked, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but what defines champions? They prevail," the victor stated in the ring as he was greeted with boos from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with his previous opponent in February - to claim a 20th career victory.
Some ringside observers felt the challenger, 31, deserved the decision but the British boxer endured the second loss of his 28-bout career.
Buatsi Earns Victory in Slow Match
The fighter's advancement has slowed in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under recent support.
He opened tentatively, with neither fighter ready to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was participating in his second bout at light heavyweight.
By the middle rounds, Parker had made it competitive, causing problems for the favorite, who worked behind a protective stance to narrowly win the cleaner rounds.
The spectators' acceptance wore thin because of regular grabbing, with Parker slipping to the canvas various instances during close exchanges.
Parker ended stronger, but several stanzas were difficult to score. However, former world champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Rea by divided decision in a terrific Manchester vs Manchester battle to capture the European light heavyweight title.
The venue fell silent for a deeply poignant memorial before the fight as 10 bells sounded in honor of local hero Hatton, who succumbed at age 46 in last month.
It was the first major televised match card in the city since Hatton's death. As the final chime disappeared, the stillness transitioned to a roar of "there's only one Hatton".
The competition during the bout matched the sentiment. Arthur was sent to the canvas by a left hook squarely on the jaw in the second round, getting up unsteadily to his feet on the eight count.
But the traditional red equipment of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was damaged soon, noticeable damage developing under his eye as the fighters traded powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the pace seldom decreased over the full distance.
The victor narrowly won the result with official scores of even score, narrow lead and 115-112, but the two athletes were persistent and courageous, everything their inspiration Hatton embodied.
