British light heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a competitive 10-round fight at the boxing arena.
But Parker found success, delivering effective single shots in a fight where the styles didn't complement each other, with constant grabbing spoiling the contest.
Two judges scored it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They win," the victor said in the arena as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts believed Parker, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-fight professional journey.
Buatsi Earns Victory in Uneventful Affair
His career development has slowed in recent years through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to take risks in a cagey early stages.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had kept it close, causing problems for Buatsi, who worked behind a tight guard to narrowly win the cleaner rounds.
The crowd's patience diminished amid regular grabbing, with Parker falling to the floor several times during close exchanges.
The underdog finished the stronger, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor moves on, but with the caliber of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Hatton Tribute Motivates All-Manchester Fight
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a terrific Manchester vs Manchester battle to capture the European light heavyweight championship.
The venue became quiet for a extremely emotional tribute before the fight as ten bells sounded in remembrance of local hero Ricky Hatton, who passed away aged 46 in last month.
It was the premier televised fight night in the city since Hatton's death. As the concluding sound ended, the silence gave way to a roar of "there's only one Hatton".
The competition during the bout matched the emotion. The eventual winner was knocked down by a powerful punch directly to the jaw in the second round, rising shakily to his feet on the referee's count.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was injured early, significant bruising developing under his eye as the pair traded punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over the full distance.
The victor edged the verdict with scoring tallies of draw, 115-113 and 115-112, but each competitor were relentless and courageous, exactly what their inspiration the legend embodied.
