UK light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a majority decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker had his moments, connecting with powerful clean blows in a fight where the approaches didn't complement each other, with excessive holding disrupting the action.
The scoring judges had it 96-94 to Buatsi, with the third a even score.
"It wasn't my best showing but what do champions do? They win," the victor commented in the ringside as he was met by negative reactions from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Some ringside observers believed the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter experienced the second setback of his 28-match professional journey.
The Champion Earns Triumph in Slow Affair
Buatsi's progress has stalled in recent times through management issues and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with the two boxers prepared to be aggressive in a tentative initial rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was making just his second appearance at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a solid defense to edge the better rounds.
The crowd's patience decreased because of frequent holding, with the challenger slipping to the canvas several times during grappling.
The underdog finished the stronger, but several stanzas were hard to judge. Although, previous titleholder Carl Frampton - working with Dazn - had it particularly wide for the challenger, giving Buatsi just one round.
The victor moves on, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester contest to secure the European light heavyweight title.
The stadium grew hushed for a profoundly moving memorial prior to the bout as ten bells sounded in remembrance of the city's native Ricky Hatton, who passed away 46 years old in September.
It was the first major televised match card in the city since the passing of Hatton. As the last bell ended, the quiet gave way to a roar of "there's just one Hatton".
The fighting inside the ropes matched the feeling. Arthur was floored by a significant blow squarely on the jaw in the early round, standing uncertainly to his feet on the count of eight.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was injured quickly, significant bruising forming under his orbital area as the fighters landed punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with effective uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the decision with official scores of 114-114, close margin and clearer margin, but both fighters were determined and full of heart, all the qualities their idol the legend embodied.
