British light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to his career under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight 10-round bout at the Manchester venue.
But the challenger found success, connecting with powerful clean blows in a fight where the techniques didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges had it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They succeed," Buatsi commented in the ringside as he was faced negative reactions from the spectators.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the decision but the Derbyshire fighter experienced the second defeat of his 28-match career.
Buatsi Secures Win in Slow Encounter
Buatsi's progress has stalled in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to realize his potential - maybe in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with the two boxers willing to take risks in a cagey opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second appearance at light-heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to edge the better periods.
The audience's tolerance wore thin during constant clinching, with the challenger going down various instances during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. Although, ex-champion Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
The victor advances, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Motivates Local Rivalry Contest
In the supporting bout, Lyndon Arthur defeated Rea by split-decision in a outstanding local rivalry contest to win the European light-heavyweight title.
The arena grew hushed for a deeply poignant homage ahead of the contest as a bell ceremony rang in memory of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the initial significant broadcast match card in the city since the passing of Hatton. As the last bell ended, the quiet transitioned to a chant of "only one Ricky Hatton".
The action inside the ropes matched the sentiment. The eventual winner was floored by a powerful punch directly to the chin in the initial stage, standing uncertainly to his position on the referee's count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up soon, noticeable damage appearing under his face as the pair traded powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the intensity seldom decreased over the full distance.
Arthur barely secured the result with official scores of 114-114, 115-113 and clearer margin, but the two athletes were persistent and courageous, exactly what their idol the legend embodied.
