British light-heavyweight Joshua Buatsi secured a victory yet unimpressive start to life under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a close ten-round fight at the boxing arena.
But Parker had his moments, landing some telling single shots in a match where the techniques didn't complement each other, with excessive holding spoiling the contest.
The scoring judges judged it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my finest showing but what do champions do? They prevail," Buatsi said in the ring as he was faced negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a twentieth professional win.
Some ringside observers thought the challenger, 31, deserved the win but the contender suffered the second defeat of his 28-match professional journey.
Buatsi Earns Triumph in Dull Affair
The fighter's advancement has slowed in the past few years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under recent support.
He started carefully, with both competitors willing to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second fight at light-heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who operated with a solid defense to narrowly win the cleaner rounds.
The spectators' acceptance decreased amid regular grabbing, with the challenger falling to the floor various instances during close exchanges.
The underdog closed well, but several stanzas were difficult to score. However, ex-champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Memorial Fuels All-Manchester Fight
In the supporting bout, Arthur defeated Rea by split-decision in a terrific all-Manchester contest to win the European light heavyweight title.
The venue fell silent for a profoundly moving memorial ahead of the contest as 10 bells rang in honor of the city's native Hatton, who passed away at age 46 in September.
It was the premier televised match card in the city since the passing of Hatton. As the last bell ended, the stillness transitioned to a chant of "only one Ricky Hatton".
The action inside the ropes reflected the feeling. Arthur was sent to the canvas by a significant blow squarely on the face in the early round, getting up unsteadily to his position on the count of eight.
But the red-colored shorts of Arthur soon came forward again. Across the ring, Rea - in competitive blue - was marked up early, noticeable damage developing under his orbital area as the fighters exchanged hard punches.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the intensity seldom decreased over 12 rounds.
The victor narrowly won the result with scoring tallies of 114-114, 115-113 and wider gap, but each competitor were persistent and full of heart, exactly what their idol Hatton stood for.
