British light-heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a split decision in a close ten-round bout at the Manchester venue.
But Parker had his moments, delivering effective clean blows in a match where the styles never quite clicked, with constant grabbing spoiling the action.
The scoring judges had it 96-94 to the winner, with the third a 95-95.
"It wasn't my finest performance but what defines champions? They win," Buatsi commented in the arena as he was greeted with disapproval from the audience.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers thought Parker, 31, merited the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
Buatsi Earns Triumph in Slow Match
The fighter's advancement has plateaued in recent years through promotional disputes and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to take risks in a cagey initial rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for Buatsi, who operated with a protective stance to barely take the more effective periods.
The spectators' acceptance diminished because of regular grabbing, with Parker going down several times during clinches.
Parker ended stronger, but many rounds were hard to judge. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just one round.
The victor advances, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Contest
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a outstanding local rivalry fight to capture the European light-heavyweight championship.
The arena became quiet for a deeply poignant tribute before the fight as a bell ceremony sounded in remembrance of local hero Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast boxing event in the city since Hatton's passing. As the final chime disappeared, the quiet transitioned to a roar of "there's only one Ricky Hatton".
The competition within the ring matched the sentiment. Arthur was knocked down by a significant blow flush on the chin in the second round, rising shakily to his feet on the referee's count.
But the Manchester United-red equipment of the fighter soon came forward again. Across the ring, the opponent - in opposing blue - was damaged soon, significant bruising forming under his orbital area as the pair exchanged powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the action hardly diminished over the full distance.
The victor narrowly won the decision with official scores of 114-114, close margin and clearer margin, but both fighters were persistent and full of heart, everything their hero Hatton embodied.
