British light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a close 10-round contest at the boxing arena.
But the challenger found success, landing some telling individual punches in a fight where the styles didn't complement each other, with constant grabbing spoiling the action.
The officials had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," the victor commented in the ring as he was greeted with negative reactions from the crowd.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Various analysts thought the challenger, 31, merited the decision but the contender experienced the second setback of his 28-fight professional journey.
The Champion Secures Victory in Uneventful Match
Buatsi's progress has plateaued in recent years through management issues and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what appears to be a final roll of the dice - under fresh management.
He started carefully, with neither fighter ready to overcommit in a cagey opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who utilized a solid defense to barely take the cleaner periods.
The crowd's patience wore thin because of frequent holding, with the challenger slipping to the canvas several times during clinches.
The underdog finished the stronger, but multiple periods were challenging to assess. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels All-Manchester Contest
In the co-main event, Arthur defeated Rea by close verdict in a terrific Manchester vs Manchester battle to win the continental belt.
The arena fell silent for a extremely emotional homage ahead of the contest as a bell ceremony sounded in memory of Manchester's own Ricky Hatton, who passed away aged 46 in September.
It was the premier televised match card in the city since Hatton's passing. As the final chime disappeared, the quiet transitioned to a roar of "only one Ricky Hatton".
The competition during the bout equaled the feeling. The eventual winner was floored by a left hook directly to the face in the early round, rising shakily to his position on the referee's count.
But the red-colored attire of Arthur soon came forward again. Across the ring, Rea - in rival City blue - was injured soon, noticeable damage forming under his eye as the fighters exchanged punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
The victor edged the verdict with official scores of 114-114, narrow lead and 115-112, but both fighters were determined and courageous, everything their idol Hatton embodied.
