British light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to his career under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker found success, landing some telling single shots in a match where the styles failed to mesh, with constant grabbing spoiling the contest.
The scoring judges had it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi commented in the ringside as he was greeted with disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to earn a 20th career victory.
Some ringside observers thought the challenger, thirty-one, merited the win but the contender endured the second defeat of his 28-fight professional journey.
The Champion Secures Triumph in Slow Match
His career development has plateaued in the past few years through contract problems and long spells of inactivity.
Once tipped as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a last chance - under recent support.
He began cautiously, with both competitors prepared to overcommit in a calculated early stages.
The challenger, 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 appearance at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to edge the more effective periods.
The spectators' acceptance wore thin because of constant clinching, with the challenger falling to the floor multiple occasions during grappling.
Parker finished the stronger, but multiple periods were difficult to score. Nevertheless, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Hatton Homage Fuels Local Rivalry Battle
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a excellent local rivalry fight to secure the European light heavyweight title.
The arena grew hushed for a profoundly moving homage prior to the bout as ten bells tolled in remembrance of local hero Hatton, who succumbed at age 46 in last month.
It was the first major televised boxing event in the urban center since Hatton's passing. As the final chime faded, the stillness transitioned to a roar of "only one Hatton".
The fighting within the ring equaled the feeling. The eventual winner was knocked down by a powerful punch flush on the face in the early round, rising shakily to his footing on the count of eight.
But the Manchester United-red attire of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was damaged quickly, significant bruising appearing under his face as the fighters landed hard punches.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the action rarely dropped over the full distance.
The victor narrowly won the verdict with scoring tallies of even score, narrow lead and clearer margin, but both fighters were persistent and brave, all the qualities their inspiration Hatton embodied.
