British light-heavyweight Joshua Buatsi made a winning yet unimpressive start to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close ten-round fight at the Co-op Live Arena.
But the challenger found success, delivering effective individual punches in a match where the approaches failed to mesh, with constant grabbing disrupting the fight.
The officials had it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi commented in the ring as he was met by negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th career victory.
Some ringside observers thought the challenger, 31, should have been awarded the victory but the Derbyshire fighter endured the second setback of his 28-fight professional journey.
Buatsi Earns Triumph in Dull Match
The fighter's advancement has plateaued in recent years through contract problems and long spells of lack of fights.
Previously predicted as the rising talent of UK boxing, he now stands trying to realize his potential - perhaps in what feels like a last chance - under recent support.
He started carefully, with both competitors ready to take risks in a cagey early stages.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, making life awkward for Buatsi, who utilized a protective stance to narrowly win the cleaner periods.
The spectators' acceptance wore thin during frequent holding, with the challenger falling to the floor several times during clinches.
The underdog closed well, but many rounds were difficult to score. However, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi moves on, but with the likes of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Hatton Memorial Inspires Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Rea by close verdict in a outstanding all-Manchester battle to secure the European light-heavyweight title.
The venue became quiet for a profoundly moving homage prior to the bout as ten bells sounded in honor of local hero Ricky Hatton, who passed away 46 years old in last month.
It was the first major televised fight night in the city since Hatton's death. As the final chime ended, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The action inside the ropes equaled the sentiment. The eventual winner was floored by a significant blow directly to the chin in the initial stage, rising shakily to his footing on the eight count.
But the Manchester United-red attire of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was marked up early, heavy swelling developing under his eye as the pair exchanged hard punches.
The challenger, 27, landed power punches but the champion, 34, responded in kind with effective uppercuts as the action hardly diminished over 12 rounds.
The victor edged the decision with official scores of even score, narrow lead and 115-112, but both fighters were persistent and full of heart, everything their hero the legend embodied.
