British light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the styles failed to mesh, with frequent clinching spoiling the action.
The scoring judges had it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi said in the ring as he was greeted with disapproval from the spectators.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Various analysts believed the challenger, 31, deserved the decision but the contender suffered the second defeat of his 28-match professional journey.
Buatsi Earns Victory in Dull Match
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to realize his potential - perhaps in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to overcommit in a cagey initial rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for Buatsi, who operated with a solid defense to barely take the better stanzas.
The spectators' acceptance decreased during frequent holding, with Parker slipping to the canvas multiple occasions during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher Benavidez, and Russian champion Bivol leading the category, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Inspires Local Rivalry Battle
In the co-main event, Arthur overcame Rea by close verdict in a excellent local rivalry battle to win the European light-heavyweight title.
The stadium grew hushed for a deeply poignant memorial prior to the bout as a bell ceremony tolled in remembrance of local hero Ricky Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the concluding sound disappeared, the silence gave way to a chant of "there's just one Ricky Hatton".
The action within the ring matched the sentiment. Arthur was floored by a left hook flush on the face in the initial stage, rising shakily to his footing on the count of eight.
But the Manchester United-red attire of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured quickly, noticeable damage forming under his face as the fighters traded punishing blows.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the pace rarely dropped over twelve rounds.
The victor edged the verdict with official scores of draw, narrow lead and wider gap, but both fighters were persistent and courageous, everything their hero the legend stood for.
