UK light-heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a competitive 10-round fight at the boxing arena.
But Parker had his moments, landing some telling single shots in a match where the techniques never quite clicked, with constant grabbing disrupting the contest.
Two judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest display but what do champions do? They succeed," the victor commented in the ringside as he was faced disapproval from the crowd.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to secure a 20th career victory.
Several boxing experts felt Parker, 31, merited the decision but the contender experienced the second setback of his 28-match professional journey.
Buatsi Claims Win in Dull Match
Buatsi's progress has slowed in recent years through management issues and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now stands trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under recent support.
He began cautiously, with both competitors prepared to take risks in a calculated initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second bout at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who utilized a solid defense to edge the cleaner rounds.
The audience's tolerance decreased amid regular grabbing, with Parker going down several times during grappling.
Parker closed well, but many rounds were hard to judge. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Homage Fuels All-Manchester Contest
In the co-main event, Arthur beat Bradley Rea by split-decision in a terrific all-Manchester contest to win the European light heavyweight championship.
The arena became quiet for a profoundly moving tribute before the fight as a bell ceremony rang in honor of the city's native Ricky Hatton, who succumbed aged 46 in last month.
It was the first major televised fight night in the location since the passing of Hatton. As the final chime disappeared, the quiet gave way to a shout of "there's just one Hatton".
The action during the bout matched the sentiment. The eventual winner was floored by a powerful punch directly to the face in the initial stage, rising shakily to his feet on the count of eight.
But the traditional red shorts of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was injured soon, significant bruising appearing under his face as the fighters exchanged punishing blows.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur edged the verdict with scoring tallies of 114-114, close margin and 115-112, but the two athletes were persistent and brave, exactly what their inspiration Hatton embodied.
