UK light heavyweight Joshua Buatsi made a winning yet unimpressive start to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a competitive ten-round fight at the Co-op Live Arena.
But the challenger had his moments, delivering effective individual punches in a match where the styles didn't complement each other, with constant grabbing marring the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my best display but how do champions respond? They succeed," Buatsi said in the arena as he was met by disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, should have been awarded the victory but the contender experienced the second setback of his 28-bout professional journey.
Buatsi Secures Victory in Uneventful Encounter
Buatsi's progress has plateaued in recent years through management issues and long spells of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to realize his potential - perhaps in what seems like a last chance - under recent support.
He started carefully, with the two boxers prepared to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the middle rounds, the underdog had made it competitive, causing problems for Buatsi, who utilized a tight guard to edge the better rounds.
The audience's tolerance diminished during constant clinching, with the challenger going down various instances during grappling.
Parker closed well, but many rounds were hard to judge. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian star Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Battle
In the supporting bout, Lyndon Arthur defeated Bradley Rea by divided decision in a excellent Manchester vs Manchester contest to secure the European light-heavyweight belt.
The arena became quiet for a profoundly moving memorial ahead of the contest as ten bells rang in remembrance of local hero Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the city since Hatton's death. As the concluding sound ended, the silence gave way to a roar of "there's just one Hatton".
The competition within the ring matched the sentiment. The eventual winner was knocked down by a left hook squarely on the chin in the second round, standing uncertainly to his feet on the eight count.
But the traditional red attire of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was marked up early, significant bruising developing under his face as the pair traded punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with powerful upward punches as the intensity rarely dropped over 12 rounds.
The victor edged the decision with official scores of 114-114, close margin and clearer margin, but the two athletes were determined and courageous, exactly what their idol Hatton represented.
