UK light heavyweight Buatsi secured a victory yet unimpressive beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a majority decision in a close 10-round contest at the boxing arena.
But the challenger found success, landing some telling clean blows in a contest where the approaches failed to mesh, with constant grabbing spoiling the contest.
Two judges judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest display but what defines champions? They win," the victor commented in the ring as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers thought the challenger, 31, merited the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
Buatsi Claims Victory in Dull Affair
The fighter's advancement has plateaued in recent times through management issues and long spells of lack of fights.
Earlier forecast as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what appears to be a last chance - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in 2022 after suffering a hand injury during the bout, was participating in his second appearance at light-heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who operated with a solid defense to barely take the cleaner periods.
The crowd's patience diminished during frequent holding, with Parker falling to the floor various instances during clinches.
Parker finished the stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
The victor moves on, but with the likes of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Fuels Local Rivalry Contest
In the secondary fight, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester contest to win the European light-heavyweight championship.
The arena fell silent for a profoundly moving tribute prior to the bout as ten bells sounded in memory of Manchester's own Ricky Hatton, who passed away aged 46 in recently.
It was the first major televised match card in the city since the passing of Hatton. As the final chime disappeared, the stillness transitioned to a chant of "there's just one Hatton".
The action inside the ropes matched the sentiment. Arthur was floored by a left hook flush on the chin in the early round, getting up unsteadily to his footing on the referee's count.
But the red-colored attire of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was injured soon, heavy swelling forming under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with effective uppercuts as the pace seldom decreased over the full distance.
Arthur narrowly won the decision with judges scorecards of draw, narrow lead and 115-112, but the two athletes were relentless and brave, all the qualities their hero Hatton embodied.
