British light heavyweight Joshua Buatsi earned a win yet underwhelming start to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight 10-round contest at the Manchester venue.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the techniques failed to mesh, with excessive holding spoiling the action.
The scoring judges had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but what defines champions? They prevail," the victor said in the arena as he was greeted with disapproval from the spectators.
The Londoner got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Various analysts felt the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter endured the second loss of his 28-fight professional journey.
The Champion Claims Triumph in Dull Affair
The fighter's advancement has slowed in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of the British fight scene, he now is positioned trying to realize his potential - possibly in what seems like a ultimate opportunity - under recent support.
He started carefully, with both competitors willing to be aggressive in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after damaging his hand in the contest, was participating in his second bout at light-heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who operated with a protective stance to edge the cleaner stanzas.
The spectators' acceptance wore thin amid regular grabbing, with the challenger going down various instances during clinches.
The underdog finished the stronger, but multiple periods were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Russian champion Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Motivates Manchester Derby Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific local rivalry battle to win the continental championship.
The stadium grew hushed for a deeply poignant tribute before the fight as ten bells rang in memory of Manchester's own Ricky Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the last bell ended, the quiet gave way to a roar of "only one Hatton".
The action inside the ropes matched the feeling. The eventual winner was knocked down by a significant blow flush on the jaw in the second round, getting up unsteadily to his footing on the count of eight.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up soon, noticeable damage appearing under his orbital area as the duo traded powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the intensity hardly diminished over the full distance.
The victor narrowly won the decision with judges scorecards of draw, close margin and wider gap, but each competitor were relentless and brave, everything their inspiration the legend embodied.
