UK light heavyweight Joshua Buatsi made a winning yet disappointing beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a tight ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling individual punches in a fight where the styles never quite clicked, with frequent clinching marring the contest.
The scoring judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest display but what defines champions? They prevail," Buatsi said in the ringside as he was met by disapproval from the crowd.
The Londoner bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Several boxing experts felt Parker, thirty-one, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-fight career.
The Champion Claims Triumph in Dull Affair
Buatsi's progress has plateaued in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with the two boxers ready to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after breaking his hand during the bout, was making just his second appearance at the higher weight class.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who utilized a protective stance to narrowly win the better stanzas.
The spectators' acceptance diminished during constant clinching, with the challenger going down multiple occasions during close exchanges.
The underdog ended stronger, but several stanzas were hard to judge. However, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Inspires Local Rivalry Contest
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding local rivalry fight to secure the continental championship.
The arena grew hushed for a profoundly moving memorial ahead of the contest as 10 bells tolled in remembrance of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised fight night in the city since Hatton's passing. As the concluding sound faded, the silence became a chant of "there's only one Hatton".
The competition within the ring matched the sentiment. Arthur was sent to the canvas by a significant blow directly to the chin in the early round, rising shakily to his feet on the count of eight.
But the Manchester United-red equipment of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was marked up quickly, significant bruising developing under his orbital area as the fighters exchanged punishing blows.
The challenger, 27, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the action rarely dropped over the full distance.
Arthur barely secured the verdict with official scores of 114-114, narrow lead and 115-112, but each competitor were relentless and brave, everything their hero Hatton represented.
