UK light heavyweight Buatsi made a winning yet underwhelming start to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a judges' verdict in a competitive ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, landing some telling clean blows in a match where the approaches didn't complement each other, with excessive holding marring the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but what defines champions? They succeed," Buatsi commented in the arena as he was faced boos from the spectators.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, thirty-one, deserved the decision but the British boxer endured the second loss of his 28-bout career.
The Champion Secures Triumph in Uneventful Match
His career development has stalled in recent years through promotional disputes and long spells of inactivity.
Once tipped as the future of UK boxing, he now is positioned trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers willing to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second bout at light heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for the favorite, who worked behind a protective stance to edge the cleaner rounds.
The spectators' acceptance decreased because of regular grabbing, with the challenger going down several times during grappling.
Parker finished the stronger, but many rounds were challenging to assess. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi progresses, but with the caliber of power puncher David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Tribute Motivates Manchester Derby Fight
In the supporting bout, Lyndon Arthur overcame Rea by split-decision in a excellent Manchester vs Manchester battle to win the continental title.
The stadium grew hushed for a deeply poignant tribute before the fight as 10 bells rang in honor of Manchester's own Hatton, who passed away aged 46 in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the last bell ended, the silence gave way to a shout of "there's just one Hatton".
The fighting within the ring matched the sentiment. Arthur was knocked down by a left hook squarely on the chin in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red equipment of Arthur soon advanced again. Across the ring, Rea - in rival City blue - was injured early, noticeable damage developing under his eye as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over twelve rounds.
The victor barely secured the verdict with judges scorecards of draw, narrow lead and wider gap, but the two athletes were determined and courageous, everything their idol Hatton stood for.
