British light-heavyweight Buatsi made a winning yet disappointing start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a competitive 10-round fight at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful single shots in a fight where the techniques didn't complement each other, with constant grabbing marring the contest.
Two judges judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my best display but what do champions do? They win," the victor commented in the ringside as he was greeted with disapproval from the crowd.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in February - to secure a 20th pro success.
Various analysts felt the challenger, thirty-one, should have been awarded the victory but the contender endured the second loss of his 28-fight career.
Buatsi Secures Victory in Dull Affair
Buatsi's progress has plateaued in recent times through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what appears to be a last chance - under new promotional backing.
He opened tentatively, with both competitors ready to overcommit in a cagey opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was making just his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for Buatsi, who utilized a protective stance to edge the better periods.
The spectators' acceptance decreased because of constant clinching, with Parker falling to the floor various instances during clinches.
Parker closed well, but several stanzas were hard to judge. However, former world champion Carl Frampton - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor advances, but with the caliber of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a terrific all-Manchester contest to win the European light heavyweight title.
The arena grew hushed for a extremely emotional tribute ahead of the contest as 10 bells sounded in remembrance of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the first major televised match card in the urban center since Hatton's death. As the final chime faded, the quiet became a shout of "there's only one Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was floored by a significant blow flush on the face in the second round, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was marked up early, noticeable damage appearing under his eye as the fighters traded punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the pace seldom decreased over 12 rounds.
The victor narrowly won the verdict with official scores of even score, narrow lead and 115-112, but the two athletes were determined and courageous, all the qualities their inspiration Hatton embodied.
