British light-heavyweight Joshua Buatsi secured a victory yet disappointing debut to life under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a close ten-round fight at the Co-op Live Arena.
But Parker found success, delivering effective single shots in a match where the styles failed to mesh, with excessive holding spoiling the action.
Two judges had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest display but what do champions do? They prevail," Buatsi stated in the ring as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the British boxer suffered the second loss of his 28-match professional journey.
Buatsi Claims Win in Uneventful Match
His career development has plateaued in recent years through contract problems and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what seems like a final roll of the dice - under recent support.
He opened tentatively, with neither fighter ready to be aggressive in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to narrowly win the cleaner periods.
The spectators' acceptance diminished amid regular grabbing, with Parker slipping to the canvas several times during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels Manchester Derby Contest
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a terrific all-Manchester battle to capture the European light heavyweight championship.
The arena fell silent for a extremely emotional memorial prior to the bout as 10 bells rang in honor of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the first major televised boxing event in the location since Hatton's passing. As the concluding sound disappeared, the stillness gave way to a chant of "there's only one Ricky Hatton".
The competition during the bout matched the feeling. Arthur was sent to the canvas by a powerful punch flush on the face in the early round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, Rea - in opposing blue - was injured quickly, heavy swelling appearing under his face as the pair landed powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor barely secured the result with judges scorecards of draw, close margin and wider gap, but both fighters were relentless and brave, all the qualities their hero the legend stood for.
