UK light heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight ten-round fight at the Manchester venue.
But Parker had his moments, landing some telling single shots in a match where the styles didn't complement each other, with excessive holding disrupting the action.
The officials had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi commented in the arena as he was met by disapproval from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts thought the challenger, 31, deserved the win but the British boxer endured the second defeat of his 28-fight professional journey.
Buatsi Earns Triumph in Dull Encounter
The fighter's advancement has stalled in the past few years through management issues and long spells of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a last chance - under recent support.
He started carefully, with the two boxers ready to be aggressive in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second fight at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, making life awkward for the favorite, who utilized a solid defense to narrowly win the more effective rounds.
The audience's tolerance diminished because of regular grabbing, with the challenger falling to the floor multiple occasions during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester fight to win the European light-heavyweight title.
The venue grew hushed for a extremely emotional memorial ahead of the contest as 10 bells tolled in remembrance of the city's native Hatton, who succumbed aged 46 in last month.
It was the first major televised boxing event in the city since Hatton's passing. As the last bell faded, the silence became a roar of "there's just one Hatton".
The fighting during the bout equaled the sentiment. The eventual winner was knocked down by a powerful punch directly to the face in the initial stage, rising shakily to his footing on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged soon, heavy swelling appearing under his eye as the duo traded punishing blows.
Rea, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the pace rarely dropped over 12 rounds.
Arthur edged the result with scoring tallies of even score, 115-113 and 115-112, but both fighters were persistent and full of heart, everything their idol the legend embodied.
