British light heavyweight Buatsi made a winning yet disappointing debut to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a competitive ten-round bout at the Manchester venue.
But Parker found success, connecting with powerful individual punches in a match where the approaches didn't complement each other, with frequent clinching spoiling the contest.
Two judges scored it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest performance but what defines champions? They win," Buatsi said in the arena as he was greeted with disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th career victory.
Several boxing experts thought the challenger, thirty-one, merited the victory but the Derbyshire fighter endured the second defeat of his 28-match career.
Buatsi Earns Victory in Slow Encounter
His career development has plateaued in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to realize his potential - possibly in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with both competitors prepared to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who operated with a tight guard to narrowly win the better rounds.
The crowd's patience decreased amid regular grabbing, with Parker falling to the floor various instances during clinches.
Parker closed well, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
The victor advances, but with the likes of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still seems difficult.
Hatton Homage Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by close verdict in a terrific all-Manchester fight to secure the continental belt.
The arena fell silent for a deeply poignant tribute before the fight as a bell ceremony rang in honor of the city's native Ricky Hatton, who died at age 46 in last month.
It was the premier televised fight night in the urban center since Hatton's passing. As the final chime disappeared, the silence transitioned to a chant of "there's just one Ricky Hatton".
The competition during the bout equaled the feeling. Arthur was sent to the canvas by a left hook squarely on the jaw in the initial stage, standing uncertainly to his feet on the count of eight.
But the red-colored attire of the fighter soon advanced again. On the opposite side, the opponent - in competitive blue - was injured early, noticeable damage forming under his eye as the fighters exchanged hard punches.
The challenger, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over the full distance.
Arthur edged the verdict with judges scorecards of 114-114, 115-113 and 115-112, but both fighters were determined and full of heart, all the qualities their hero Hatton represented.
