UK light heavyweight Joshua Buatsi earned a win yet unimpressive start to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a competitive 10-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling clean blows in a fight where the styles didn't complement each other, with frequent clinching spoiling the contest.
The scoring judges judged it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest showing but what defines champions? They succeed," the victor stated in the ringside as he was met by negative reactions from the crowd.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Various analysts felt the challenger, thirty-one, deserved the decision but the contender experienced the second defeat of his 28-match career.
The Champion Earns Triumph in Uneventful Encounter
The fighter's advancement has plateaued in recent times through management issues and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now stands trying to achieve expectations - perhaps in what feels like a last chance - under recent support.
He began cautiously, with neither fighter willing to take risks in a calculated early stages.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to edge the cleaner stanzas.
The audience's tolerance decreased during frequent holding, with the challenger slipping to the canvas various instances during clinches.
Parker finished the stronger, but several stanzas were hard to judge. Although, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Hatton Tribute Fuels All-Manchester Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester contest to capture the European light heavyweight championship.
The venue grew hushed for a deeply poignant homage ahead of the contest as 10 bells rang in honor of the city's native Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the concluding sound ended, the silence gave way to a roar of "there's only one Hatton".
The competition within the ring reflected the emotion. The eventual winner was sent to the canvas by a significant blow squarely on the chin in the second round, getting up unsteadily to his footing on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was damaged quickly, heavy swelling appearing under his face as the pair traded punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over 12 rounds.
The victor edged the result with official scores of draw, close margin and clearer margin, but both fighters were persistent and brave, all the qualities their inspiration Hatton represented.
