UK light heavyweight Joshua Buatsi secured a victory yet underwhelming start to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a match where the styles never quite clicked, with excessive holding disrupting the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest display but what do champions do? They win," the victor said in the ringside as he was greeted with boos from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Various analysts felt Parker, 31, should have been awarded the victory but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
Buatsi Secures Victory in Slow Match
His career development has slowed in recent years through promotional disputes and extended periods of lack of fights.
Once tipped as the next star of British boxing, he now finds himself trying to realize his potential - maybe in what seems like a ultimate opportunity - under recent support.
He started carefully, with both competitors prepared to be aggressive in a calculated initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who utilized a solid defense to narrowly win the cleaner stanzas.
The audience's tolerance decreased amid frequent holding, with Parker falling to the floor various instances during close exchanges.
The underdog finished the stronger, but multiple periods were hard to judge. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi progresses, but with the caliber of heavy hitter Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Hatton Memorial Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a terrific all-Manchester fight to capture the European light-heavyweight belt.
The stadium grew hushed for a extremely emotional memorial prior to the bout as 10 bells sounded in honor of local hero Ricky Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the final chime faded, the quiet gave way to a roar of "there's just one Hatton".
The competition inside the ropes matched the sentiment. The eventual winner was knocked down by a left hook directly to the jaw in the initial stage, standing uncertainly to his feet on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up quickly, heavy swelling appearing under his orbital area as the duo exchanged punishing blows.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity seldom decreased over the full distance.
Arthur barely secured the decision with judges scorecards of even score, narrow lead and 115-112, but both fighters were determined and courageous, exactly what their hero the legend represented.
