UK light heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a competitive 10-round fight at the boxing arena.
But Parker landed significant shots, delivering effective clean blows in a fight where the techniques never quite clicked, with excessive holding marring the action.
The scoring judges judged it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what defines champions? They prevail," the victor stated in the ringside as he was met by disapproval from the audience.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts thought Parker, 31, merited the decision but the Derbyshire fighter experienced the second loss of his 28-bout professional journey.
Buatsi Earns Victory in Uneventful Match
His career development has plateaued in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, 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 opened tentatively, with neither fighter ready to take risks in a calculated early stages.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second appearance at light heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for Buatsi, who operated with a protective stance to narrowly win the more effective rounds.
The audience's tolerance wore thin during frequent holding, with the challenger slipping to the canvas several times during grappling.
Parker finished the stronger, but multiple periods were challenging to assess. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Hatton Tribute Inspires All-Manchester Battle
In the supporting bout, Arthur beat Bradley Rea by divided decision in a outstanding all-Manchester fight to win the continental belt.
The venue became quiet for a extremely emotional memorial prior to the bout as a bell ceremony sounded in remembrance of Manchester's own Hatton, who succumbed 46 years old in recently.
It was the premier televised match card in the urban center since the passing of Hatton. As the final chime disappeared, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The fighting within the ring reflected the emotion. Arthur was knocked down by a left hook squarely on the chin in the initial stage, getting up unsteadily to his feet on the eight count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, the opponent - in competitive blue - was damaged early, significant bruising forming under his eye as the fighters traded hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace hardly diminished over the full distance.
The victor barely secured the decision with official scores of even score, close margin and 115-112, but each competitor were determined and full of heart, exactly what their inspiration Hatton represented.
