British light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under new promoters with a points victory over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a majority decision in a competitive 10-round contest at the boxing arena.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the styles failed to mesh, with excessive holding spoiling the action.
Two judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but how do champions respond? They prevail," the victor stated in the ringside as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, should have been awarded the victory but the British boxer suffered the second setback of his 28-bout professional journey.
The Champion Earns Triumph in Slow Match
Buatsi's progress has plateaued in recent years through management issues and considerable time of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under recent support.
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 damaging his hand mid-fight, was making just his second appearance at light heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for the favorite, who utilized a solid defense to narrowly win the more effective periods.
The audience's tolerance diminished because of frequent holding, with the challenger going down multiple occasions during clinches.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, ex-champion Carl Frampton - working with Dazn - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Inspires All-Manchester Battle
In the co-main event, Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester contest to capture the continental title.
The venue grew hushed for a profoundly moving homage before the fight as a bell ceremony rang in memory of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the last bell disappeared, the stillness transitioned to a chant of "only one Ricky Hatton".
The competition during the bout equaled the sentiment. Arthur was floored by a left hook directly to the jaw in the initial stage, standing uncertainly to his feet on the count of eight.
But the traditional red attire of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was marked up soon, noticeable damage forming under his face as the pair traded hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the action hardly diminished over twelve rounds.
Arthur edged the result with scoring tallies of 114-114, narrow lead and clearer margin, but the two athletes were persistent and courageous, all the qualities their idol Hatton embodied.
