UK light heavyweight Joshua Buatsi earned a win yet disappointing debut to his career under recent management with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful single shots in a fight where the approaches never quite clicked, with constant grabbing disrupting the contest.
The officials judged it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my greatest performance but what do champions do? They prevail," Buatsi stated in the arena as he was faced disapproval from the audience.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a 20th pro success.
Various analysts thought the challenger, thirty-one, should have been awarded the decision but the contender experienced the second loss of his 28-bout career.
Buatsi Claims Triumph in Uneventful Affair
Buatsi's progress has plateaued in recent times through contract problems and considerable time of lack of fights.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what appears to be a last chance - under recent support.
He started carefully, with both competitors willing to be aggressive in a calculated opening few rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who utilized a protective stance to narrowly win the more effective rounds.
The audience's tolerance decreased amid frequent holding, with Parker slipping to the canvas multiple occasions during grappling.
Parker closed well, but several stanzas were challenging to assess. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Tribute Inspires All-Manchester Battle
In the secondary fight, Arthur overcame Bradley Rea by split-decision in a terrific local rivalry contest to secure the continental championship.
The arena grew hushed for a extremely emotional homage ahead of the contest as ten bells sounded in honor of local hero Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised match card in the urban center since Hatton's death. As the final chime faded, the silence became a shout of "there's just one Hatton".
The action inside the ropes reflected the emotion. Arthur was sent to the canvas by a powerful punch flush on the chin in the initial stage, rising shakily to his feet on the count of eight.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was injured soon, heavy swelling appearing under his eye as the pair exchanged punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over the full distance.
The victor barely secured the decision with scoring tallies of draw, 115-113 and wider gap, but the two athletes were persistent and full of heart, everything their idol the legend stood for.
