UK light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a tight 10-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful single shots in a match where the techniques didn't complement each other, with constant grabbing spoiling the action.
The scoring judges had it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They succeed," Buatsi stated in the ring as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Several boxing experts believed Parker, 31, should have been awarded the victory but the Derbyshire fighter endured the second setback of his 28-fight professional journey.
The Champion Claims Win in Dull Affair
His career development has slowed in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to realize his potential - possibly in what seems like a last chance - under new promotional backing.
He opened tentatively, with the two boxers ready to take risks in a tentative early stages.
Parker, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury in the contest, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to narrowly win the more effective rounds.
The spectators' acceptance diminished during constant clinching, with Parker slipping to the canvas multiple occasions during grappling.
The underdog ended stronger, but many rounds were challenging to assess. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Fuels All-Manchester Contest
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding all-Manchester contest to win the continental championship.
The arena fell silent for a profoundly moving homage prior to the bout as ten bells rang in remembrance of the city's native Hatton, who succumbed 46 years old in recently.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the silence became a roar of "only one Hatton".
The action during the bout equaled the feeling. The eventual winner was floored by a powerful punch squarely on the chin in the second round, rising shakily to his feet on the count of eight.
But the traditional red equipment of Arthur soon advanced again. From the other corner, the opponent - in competitive blue - was injured quickly, heavy swelling appearing under his orbital area as the duo exchanged punishing blows.
Rea, 27, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur edged the decision with judges scorecards of draw, narrow lead and clearer margin, but the two athletes were relentless and brave, all the qualities their inspiration Hatton stood for.
