British light-heavyweight Joshua Buatsi earned a win yet disappointing start to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a tight 10-round contest at the boxing arena.
But the challenger had his moments, connecting with powerful individual punches in a match where the approaches never quite clicked, with frequent clinching spoiling the fight.
The officials judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my greatest display but what do champions do? They succeed," the victor commented in the ring as he was met by boos from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Various analysts felt the challenger, 31, should have been awarded the decision but the contender experienced the second setback of his 28-fight career.
Buatsi Earns Win in Uneventful Affair
His career development has stalled in the past few years through management issues and extended periods of lack of fights.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to realize his potential - maybe in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers prepared to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who utilized a tight guard to barely take the cleaner periods.
The audience's tolerance wore thin because of regular grabbing, with Parker slipping to the canvas multiple occasions during grappling.
The underdog ended stronger, but several stanzas were hard to judge. Although, former world champion Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just one round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a terrific Manchester vs Manchester battle to secure the continental title.
The venue became quiet for a deeply poignant memorial before the fight as ten bells rang in remembrance of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the premier televised fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the quiet transitioned to a chant of "there's only one Ricky Hatton".
The fighting during the bout reflected the sentiment. Arthur was knocked down by a left hook directly to the jaw in the second round, rising shakily to his footing on the eight count.
But the red-colored attire of the fighter soon came forward again. On the opposite side, Rea - in rival City blue - was marked up early, significant bruising forming under his orbital area as the fighters traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the action seldom decreased over the full distance.
Arthur barely secured the decision with official scores of 114-114, close margin and wider gap, but both fighters were persistent and full of heart, all the qualities their inspiration the legend stood for.
