British light heavyweight Joshua Buatsi secured a victory yet unimpressive start to life under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive ten-round fight at the boxing arena.
But Parker found success, connecting with powerful clean blows in a fight where the techniques never quite clicked, with frequent clinching disrupting the fight.
The officials judged it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," the victor said in the ringside as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to secure a 20th career victory.
Some ringside observers thought the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter endured the second loss of his 28-match career.
The Champion Secures Victory in Dull Encounter
Buatsi's progress has plateaued in recent times through contract problems and long spells of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to achieve expectations - maybe in what seems like a last chance - under new promotional backing.
He opened tentatively, with the two boxers prepared to overcommit in a cagey opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was participating in his second fight at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, causing problems for Buatsi, who operated with a protective stance to narrowly win the better rounds.
The spectators' acceptance decreased because of frequent holding, with the challenger going down several times during close exchanges.
The underdog finished the stronger, but multiple periods were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Hatton Memorial Inspires Manchester Derby Contest
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a excellent Manchester vs Manchester fight to secure the continental championship.
The stadium fell silent for a profoundly moving homage prior to the bout as 10 bells tolled in remembrance of local hero Ricky Hatton, who succumbed at age 46 in September.
It was the premier televised boxing event in the location since the passing of Hatton. As the concluding sound ended, the stillness transitioned to a chant of "only one Ricky Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a powerful punch squarely on the face in the early round, rising shakily to his feet on the referee's count.
But the red-colored attire of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was marked up soon, significant bruising appearing under his face as the fighters landed hard punches.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity hardly diminished over twelve rounds.
Arthur barely secured the verdict with official scores of draw, close margin and wider gap, but both fighters were determined and full of heart, exactly what their idol the legend represented.
