UK light heavyweight Joshua Buatsi earned a win yet disappointing beginning to his career under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a split decision in a tight 10-round contest at the Co-op Live Arena.
But the challenger found success, connecting with powerful clean blows in a contest where the techniques failed to mesh, with constant grabbing marring the fight.
Two judges had it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my best display but what defines champions? They prevail," the victor said in the ring as he was faced negative reactions from the spectators.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers thought the challenger, 31, should have been awarded the decision but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
Buatsi Secures Triumph in Dull Encounter
His career development has plateaued in the past few years through management issues and considerable time of inactivity.
Previously predicted as the next star of UK boxing, he now is positioned trying to realize his potential - possibly in what feels like a ultimate opportunity - under fresh management.
He began cautiously, with neither fighter prepared to be aggressive in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second appearance at light heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who utilized a protective stance to narrowly win the more effective periods.
The crowd's patience diminished because of constant clinching, with the challenger going down various instances during grappling.
The underdog closed well, but multiple periods were difficult to score. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the caliber of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates Local Rivalry Fight
In the supporting bout, Arthur beat Rea by split-decision in a terrific all-Manchester battle to capture the European light-heavyweight belt.
The venue grew hushed for a deeply poignant memorial prior to the bout as ten bells rang in remembrance of Manchester's own Ricky Hatton, who died at age 46 in recently.
It was the first major televised fight night in the location since the passing of Hatton. As the final chime faded, the silence became a chant of "there's just one Ricky Hatton".
The competition inside the ropes equaled the emotion. Arthur was knocked down by a left hook directly to the face in the early round, getting up unsteadily to his feet on the eight count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged quickly, noticeable damage developing under his face as the fighters exchanged hard punches.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the action rarely dropped over the full distance.
Arthur edged the result with scoring tallies of 114-114, narrow lead and 115-112, but the two athletes were relentless and full of heart, exactly what their hero the legend stood for.
