UK light heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a tight ten-round contest at the Manchester venue.
But the challenger had his moments, delivering effective single shots in a contest where the styles didn't complement each other, with constant grabbing spoiling the fight.
The officials judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my best performance but how do champions respond? They succeed," the victor stated in the ringside as he was met by boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers believed Parker, 31, merited the decision but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
The Champion Secures Victory in Uneventful Match
His career development has plateaued in the past few years through contract problems and considerable time of lack of fights.
Earlier forecast as the next star of UK boxing, he now finds himself trying to achieve expectations - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with the two boxers willing to overcommit in a calculated early stages.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was participating in his second appearance at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for the favorite, who worked behind a tight guard to barely take the more effective periods.
The crowd's patience wore thin during regular grabbing, with Parker falling to the floor several times during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a outstanding all-Manchester fight to capture the European light-heavyweight belt.
The venue became quiet for a deeply poignant tribute prior to the bout as ten bells sounded in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound disappeared, the quiet became a shout of "only one Hatton".
The action within the ring matched the feeling. The eventual winner was floored by a significant blow directly to the jaw in the early round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up quickly, heavy swelling forming under his eye as the fighters exchanged hard punches.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the intensity seldom decreased over the full distance.
Arthur edged the decision with judges scorecards of 114-114, narrow lead and 115-112, but each competitor were determined and courageous, everything their idol Hatton stood for.
