UK light-heavyweight Joshua Buatsi secured a victory yet disappointing debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive ten-round fight at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the styles failed to mesh, with frequent clinching disrupting the contest.
The officials scored it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my finest display but what defines champions? They win," the victor stated in the ringside as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, should have been awarded the decision but the British boxer endured the second setback of his 28-match professional journey.
The Champion Secures Triumph in Slow Affair
His career development has stalled in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the rising talent of UK boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with both competitors willing to overcommit in a cagey opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after breaking his hand in the contest, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a solid defense to edge the more effective stanzas.
The crowd's patience diminished during constant clinching, with Parker falling to the floor multiple occasions during grappling.
The underdog ended stronger, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the presence of hard hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Hatton Homage Motivates Local Rivalry Fight
In the co-main event, Arthur defeated Rea by close verdict in a excellent Manchester vs Manchester contest to capture the European light-heavyweight title.
The stadium grew hushed for a profoundly moving memorial before the fight as ten bells tolled in honor of local hero Ricky Hatton, who died 46 years old in recently.
It was the first major televised match card in the urban center since Hatton's passing. As the concluding sound faded, the silence became a shout of "there's just one Ricky Hatton".
The competition during the bout equaled the feeling. Arthur was knocked down by a left hook directly to the jaw in the initial stage, standing uncertainly to his position on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was injured early, noticeable damage developing under his orbital area as the pair landed powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur barely secured the decision with scoring tallies of 114-114, 115-113 and 115-112, but the two athletes were determined and brave, all the qualities their idol Hatton stood for.
