UK light heavyweight Joshua Buatsi secured a victory yet underwhelming start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight ten-round bout at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a match where the approaches failed to mesh, with constant grabbing spoiling the contest.
The officials judged it 96-94 to the winner, with the third a even score.
"It wasn't my best performance but what defines champions? They win," the victor commented in the arena as he was faced negative reactions from the spectators.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in last winter - to earn a 20th pro success.
Several boxing experts believed the challenger, thirty-one, merited the victory but the Derbyshire fighter experienced the second setback of his 28-match career.
The Champion Earns Win in Uneventful Encounter
Buatsi's progress has slowed in recent years through management issues and long spells of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to realize his potential - perhaps in what seems like a final roll of the dice - under recent support.
He opened tentatively, with the two boxers ready to take risks 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 competing in only his second appearance at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who operated with a tight guard to barely take the more effective periods.
The spectators' acceptance wore thin during regular grabbing, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels All-Manchester Battle
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a excellent Manchester vs Manchester contest to win the European light-heavyweight belt.
The stadium became quiet for a profoundly moving tribute prior to the bout as a bell ceremony rang in honor of the city's native Ricky Hatton, who succumbed 46 years old in last month.
It was the premier televised match card in the urban center since Hatton's passing. As the concluding sound faded, the stillness gave way to a chant of "only one Hatton".
The action during the bout equaled the sentiment. Arthur was knocked down by a powerful punch directly to the chin in the initial stage, standing uncertainly to his position on the count of eight.
But the traditional red attire of Arthur soon came forward again. From the other corner, the opponent - in competitive blue - was injured quickly, heavy swelling developing under his eye as the duo traded powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over twelve rounds.
Arthur barely secured the decision with scoring tallies of 114-114, narrow lead and 115-112, but the two athletes were persistent and brave, exactly what their idol the legend represented.
