UK light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a contest where the approaches failed to mesh, with constant grabbing disrupting the action.
Two judges judged it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They prevail," Buatsi commented in the ringside as he was met by negative reactions from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to claim a 20th pro success.
Some ringside observers thought Parker, 31, merited the victory but the British boxer endured the second setback of his 28-match career.
Buatsi Claims Win in Dull Affair
His career development has plateaued in recent years through contract problems and extended periods of lack of fights.
Previously predicted as the next star of the British fight scene, he now finds himself trying to achieve expectations - maybe in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers ready to overcommit in a cagey initial rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for the favorite, who utilized a protective stance to edge the better rounds.
The spectators' acceptance diminished because of regular grabbing, with Parker falling to the floor various instances during clinches.
The underdog ended stronger, but multiple periods were hard to judge. However, former world champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Motivates All-Manchester Contest
In the secondary fight, Arthur defeated Bradley Rea by divided decision in a excellent Manchester vs Manchester battle to win the European light heavyweight belt.
The venue fell silent for a extremely emotional tribute prior to the bout as ten bells rang in honor of Manchester's own Ricky Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast fight night in the city since Hatton's passing. As the final chime faded, the silence became a roar of "only one Ricky Hatton".
The action within the ring matched the emotion. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the initial stage, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red shorts of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was marked up soon, significant bruising forming under his eye as the pair landed punishing blows.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the action rarely dropped over twelve rounds.
The victor barely secured the result with official scores of draw, close margin and clearer margin, but the two athletes were relentless and full of heart, all the qualities their idol Hatton stood for.
