UK light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a close ten-round contest at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a contest where the styles didn't complement each other, with constant grabbing marring the contest.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what defines champions? They prevail," the victor commented in the arena as he was faced boos from the spectators.
The Londoner bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Several boxing experts believed Parker, thirty-one, merited the decision but the Derbyshire fighter experienced the second loss of his 28-bout career.
Buatsi Earns Triumph in Uneventful Encounter
His career development has stalled in recent times through contract problems and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to realize his potential - maybe in what seems like a last chance - under new promotional backing.
He began cautiously, with the two boxers prepared to be aggressive in a cagey early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second bout at light-heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who utilized a solid defense to narrowly win the cleaner stanzas.
The audience's tolerance diminished because of regular grabbing, with the challenger falling to the floor various instances during grappling.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Hatton Homage Motivates Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Bradley Rea by close verdict in a outstanding local rivalry contest to win the European light-heavyweight championship.
The arena grew hushed for a deeply poignant homage ahead of the contest as 10 bells rang in memory of the city's native Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the concluding sound ended, the silence transitioned to a roar of "only one Ricky Hatton".
The competition during the bout matched the emotion. The eventual winner was sent to the canvas by a left hook squarely on the chin in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red attire of the fighter soon pressed ahead again. On the opposite side, Rea - in competitive blue - was injured quickly, noticeable damage developing under his orbital area as the fighters traded powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the action hardly diminished over twelve rounds.
Arthur narrowly won the result with official scores of even score, narrow lead and clearer margin, but both fighters were relentless and full of heart, exactly what their inspiration Hatton stood for.
