British light-heavyweight Joshua Buatsi earned a win yet underwhelming start to life under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a tight ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a contest where the techniques failed to mesh, with frequent clinching spoiling the action.
The officials had it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but what do champions do? They succeed," Buatsi said in the arena as he was met by disapproval from the spectators.
The Londoner bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Several boxing experts thought the challenger, thirty-one, merited the win but the Derbyshire fighter endured the second setback of his 28-match professional journey.
The Champion Claims Victory in Slow Encounter
Buatsi's progress has stalled in recent years through management issues and long spells of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what appears to be a last chance - under fresh management.
He began cautiously, with the two boxers ready to take risks in a cagey initial rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was making just his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a protective stance to barely take the better periods.
The crowd's patience decreased amid regular grabbing, with Parker slipping to the canvas multiple occasions during clinches.
Parker closed well, but several stanzas were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the likes of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Hatton Tribute Inspires Manchester Derby Contest
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to win the European light-heavyweight championship.
The venue fell silent for a profoundly moving homage prior to the bout as 10 bells rang in honor of local hero Hatton, who succumbed 46 years old in recently.
It was the first major televised fight night in the city since Hatton's passing. As the concluding sound faded, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The fighting within the ring matched the emotion. Arthur was knocked down by a significant blow squarely on the chin in the early round, getting up unsteadily to his feet on the referee's count.
But the red-colored equipment of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was marked up soon, noticeable damage developing under his orbital area as the duo landed punishing blows.
The challenger, 27, delivered effective strikes but Arthur, 34, matched the intensity with effective uppercuts as the intensity seldom decreased over the full distance.
The victor barely secured the verdict with official scores of draw, narrow lead and wider gap, but both fighters were relentless and courageous, all the qualities their inspiration the legend stood for.
