UK light-heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a tight 10-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful clean blows in a contest where the styles never quite clicked, with excessive holding spoiling the action.
The officials judged it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," Buatsi said in the arena as he was faced boos from the spectators.
The Londoner bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to earn a 20th pro success.
Various analysts felt the challenger, 31, deserved the decision but the Derbyshire fighter endured the second defeat of his 28-fight career.
Buatsi Earns Triumph in Uneventful Match
His career development has plateaued in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under recent support.
He began cautiously, with both competitors willing to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand during the bout, was participating in his second bout at light-heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who utilized a tight guard to narrowly win the cleaner stanzas.
The spectators' acceptance wore thin because of regular grabbing, with Parker falling to the floor several times during close exchanges.
Parker closed well, but multiple periods were hard to judge. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
Buatsi advances, but with the likes of hard hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the secondary fight, Arthur defeated Bradley Rea by divided decision in a terrific all-Manchester contest to secure the European light heavyweight championship.
The venue grew hushed for a extremely emotional memorial ahead of the contest as 10 bells rang in honor of Manchester's own Ricky Hatton, who succumbed at age 46 in recently.
It was the first major televised match card in the city since Hatton's death. As the final chime faded, the stillness transitioned to a chant of "there's just one Hatton".
The fighting within the ring reflected the emotion. The eventual winner was knocked down by a left hook directly to the chin in the early round, standing uncertainly to his feet on the referee's count.
But the red-colored attire of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was damaged early, noticeable damage forming under his eye as the duo traded punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the pace hardly diminished over 12 rounds.
Arthur narrowly won the result with scoring tallies of 114-114, close margin and wider gap, but the two athletes were determined and full of heart, all the qualities their inspiration the legend represented.
