UK light-heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a close ten-round contest at the boxing arena.
But the challenger had his moments, landing some telling clean blows in a contest where the styles didn't complement each other, with excessive holding spoiling the contest.
Two judges had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but what do champions do? They succeed," the victor stated in the ringside as he was greeted with disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Some ringside observers believed the challenger, thirty-one, merited the win but the contender endured the second defeat of his 28-fight career.
The Champion Claims Victory in Slow Encounter
Buatsi's progress has slowed in recent years through contract problems and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with neither fighter willing to take risks in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was making just his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, making life awkward for the favorite, who worked behind a tight guard to narrowly win the more effective periods.
The spectators' acceptance diminished amid frequent holding, with Parker falling to the floor several times during clinches.
Parker closed well, but several stanzas were hard to judge. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels Local Rivalry Battle
In the co-main event, Arthur overcame Bradley Rea by close verdict in a excellent all-Manchester contest to win the continental belt.
The arena became quiet for a profoundly moving homage ahead of the contest as a bell ceremony rang in remembrance of local hero Ricky Hatton, who died aged 46 in recently.
It was the premier televised boxing event in the urban center since Hatton's passing. As the concluding sound faded, the silence transitioned to a shout of "there's just one Ricky Hatton".
The action within the ring equaled the feeling. The eventual winner was sent to the canvas by a significant blow squarely on the face in the initial stage, getting up unsteadily to his footing on the eight count.
But the traditional red equipment of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was injured soon, significant bruising forming under his orbital area as the duo traded punishing blows.
Rea, 27, connected with strong blows but Arthur, 34, matched the intensity with stinging uppercuts as the action seldom decreased over the full distance.
Arthur edged the verdict with scoring tallies of 114-114, narrow lead and clearer margin, but the two athletes were persistent and full of heart, exactly what their idol the legend represented.
