British light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a close ten-round contest at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a fight where the styles failed to mesh, with excessive holding marring the contest.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my best display but what defines champions? They succeed," the victor said in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
The Champion Claims Victory in Dull Affair
The fighter's advancement has stalled in recent times through management issues and considerable time of lack of fights.
Once tipped as the next star of UK boxing, he now stands trying to fulfil that early promise - possibly in what appears to be a last chance - under recent support.
He began cautiously, with both competitors willing to be aggressive in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who worked behind a protective stance to narrowly win the better rounds.
The audience's tolerance diminished amid constant clinching, with Parker falling to the floor several times during grappling.
The underdog finished the stronger, but several stanzas were difficult to score. However, previous titleholder Carl Frampton - working with Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates Local Rivalry Contest
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding Manchester vs Manchester contest to win the continental belt.
The arena fell silent for a extremely emotional memorial before the fight as a bell ceremony sounded in remembrance of Manchester's own Ricky Hatton, who died at age 46 in last month.
It was the premier televised fight night in the location since Hatton's passing. As the final chime ended, the quiet transitioned to a roar of "there's just one Hatton".
The action inside the ropes matched the sentiment. Arthur was knocked down by a left hook directly to the jaw in the initial stage, rising shakily to his feet on the referee's count.
But the Manchester United-red shorts of the fighter soon came forward again. On the opposite side, Rea - in opposing blue - was marked up soon, heavy swelling appearing under his face as the fighters landed hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the decision with official scores of draw, 115-113 and 115-112, but both fighters were relentless and courageous, everything their idol the legend stood for.
