UK 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 punch output appeared to earn him a judges' verdict in a tight ten-round contest at the Manchester venue.
But the challenger found success, landing some telling individual punches in a match where the approaches didn't complement each other, with frequent clinching disrupting the contest.
The scoring judges had it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my best display but what do champions do? They prevail," the victor commented in the arena as he was greeted with disapproval from the audience.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Various analysts believed the challenger, thirty-one, merited the decision but the British boxer endured the second defeat of his 28-match professional journey.
The Champion Secures Victory in Uneventful Encounter
His career development has slowed in recent years through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a final roll of the dice - under fresh management.
He started carefully, with the two boxers prepared to take risks in a tentative opening few rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand during the bout, was participating in his second appearance at light heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who worked behind a protective stance to edge the cleaner rounds.
The spectators' acceptance diminished amid constant clinching, with the challenger slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
The victor advances, but with the presence of heavy hitter Benavidez, and Russian champion Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the co-main event, Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester fight to secure the European light heavyweight championship.
The stadium fell silent for a deeply poignant memorial before the fight as ten bells sounded in memory of local hero Ricky Hatton, who died aged 46 in last month.
It was the initial significant broadcast match card in the city since Hatton's passing. As the last bell disappeared, the quiet became a chant of "there's only one Ricky Hatton".
The fighting within the ring reflected the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the jaw in the early round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red attire of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was damaged quickly, significant bruising developing under his face as the duo exchanged punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over the full distance.
Arthur narrowly won the verdict with scoring tallies of 114-114, 115-113 and 115-112, but the two athletes were relentless and courageous, everything their inspiration the legend stood for.
