British light-heavyweight Joshua Buatsi earned a win yet underwhelming debut to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a tight ten-round fight at the Manchester venue.
But the challenger found success, delivering effective individual punches in a contest where the approaches didn't complement each other, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the ring as he was met by negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a 20th pro success.
Various analysts thought Parker, thirty-one, should have been awarded the win but the British boxer endured the second defeat of his 28-bout career.
Buatsi Earns Victory in Slow Encounter
Buatsi's progress has plateaued in recent years through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now stands trying to realize his potential - maybe in what seems like a last chance - under fresh management.
He started carefully, with neither fighter willing to overcommit in a calculated initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after breaking his hand during the bout, was making just his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a solid defense to narrowly win the more effective periods.
The crowd's patience decreased because of frequent holding, with Parker going down various instances during close exchanges.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Tribute Inspires Local Rivalry Fight
In the co-main event, Arthur beat Bradley Rea by divided decision in a excellent all-Manchester contest to win the European light heavyweight belt.
The stadium fell silent for a deeply poignant homage ahead of the contest as ten bells tolled in honor of the city's native Hatton, who died at age 46 in September.
It was the first major televised boxing event in the location since Hatton's passing. As the last bell disappeared, the quiet became a chant of "only one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was sent to the canvas by a left hook directly to the face in the second round, standing uncertainly to his feet on the count of eight.
But the red-colored attire of Arthur soon pressed ahead again. Across the ring, Rea - in opposing blue - was damaged early, heavy swelling developing under his orbital area as the pair landed powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the action hardly diminished over 12 rounds.
The victor barely secured the decision with scoring tallies of even score, close margin and 115-112, but both fighters were determined and brave, everything their inspiration Hatton embodied.
