British light-heavyweight Buatsi earned a win yet unimpressive start to his career under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight ten-round contest at the boxing arena.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the techniques failed to mesh, with frequent clinching marring the contest.
Two judges judged it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest performance but what defines champions? They prevail," Buatsi commented in the ringside as he was met by boos from the spectators.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Several boxing experts believed Parker, thirty-one, deserved the win but the Derbyshire fighter experienced the second setback of his 28-bout professional journey.
The Champion Secures Win in Dull Affair
Buatsi's progress has slowed in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under fresh management.
He started carefully, with the two boxers willing to be aggressive in a calculated initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand in the contest, was making just his second bout at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to edge the better stanzas.
The crowd's patience decreased during frequent holding, with the challenger slipping to the canvas various instances during clinches.
Parker finished the stronger, but multiple periods were hard to judge. However, ex-champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Arthur beat Bradley Rea by split-decision in a excellent local rivalry contest to capture the continental belt.
The stadium fell silent for a extremely emotional tribute before the fight as 10 bells rang in memory of the city's native Hatton, who passed away 46 years old in September.
It was the premier televised match card in the location since the passing of Hatton. As the last bell ended, the stillness gave way to a shout of "there's only one Hatton".
The fighting during the bout matched the feeling. Arthur was knocked down by a powerful punch flush on the chin in the early round, standing uncertainly to his feet on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was damaged quickly, noticeable damage forming under his orbital area as the pair traded hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, 34, responded in kind with stinging uppercuts as the action rarely dropped over twelve rounds.
The victor edged the decision with scoring tallies of even score, narrow lead and 115-112, but each competitor were relentless and courageous, all the qualities their idol the legend stood for.
