British light-heavyweight Joshua Buatsi earned a win yet underwhelming debut to life under fresh promotional backing with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a close 10-round bout at the boxing arena.
But the challenger found success, landing some telling individual punches in a match where the styles never quite clicked, with excessive holding marring the fight.
Two judges had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi commented in the ringside as he was met by negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the decision but the British boxer suffered the second defeat of his 28-bout professional journey.
The Champion Secures Win in Uneventful Match
The fighter's advancement has stalled in recent times through contract problems and extended periods of inactivity.
Earlier forecast 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 fresh management.
He began cautiously, with neither fighter prepared to overcommit in a tentative opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had kept it close, making life awkward for the favorite, who operated with a tight guard to narrowly win the better periods.
The crowd's patience decreased during frequent holding, with the challenger slipping to the canvas various instances during grappling.
The underdog finished the stronger, but several stanzas were difficult to score. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Memorial Fuels Local Rivalry Battle
In the supporting bout, Arthur defeated Rea by split-decision in a outstanding Manchester vs Manchester fight to capture the continental title.
The arena grew hushed for a extremely emotional tribute before the fight as a bell ceremony tolled in memory of the city's native Hatton, who died 46 years old in recently.
It was the premier televised fight night in the location since Hatton's death. As the last bell faded, the silence became a chant of "only one Hatton".
The fighting during the bout equaled the feeling. Arthur was floored by a left hook flush on the chin in the second round, standing uncertainly to his footing on the eight count.
But the Manchester United-red attire of the fighter soon pressed ahead again. From the other corner, Rea - in competitive blue - was damaged quickly, noticeable damage developing under his orbital area as the pair exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace seldom decreased over the full distance.
Arthur edged the decision with official scores of 114-114, 115-113 and 115-112, but each competitor were persistent and brave, all the qualities their idol Hatton represented.
