UK light-heavyweight Buatsi secured a victory yet unimpressive debut to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a competitive 10-round fight at the Co-op Live Arena.
But Parker had his moments, landing some telling clean blows in a fight where the styles never quite clicked, with excessive holding spoiling the action.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They succeed," Buatsi stated in the ring as he was met by disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts felt Parker, thirty-one, should have been awarded the win but the Derbyshire fighter endured the second defeat of his 28-fight career.
The Champion Secures Victory in Dull Encounter
Buatsi's progress has stalled in recent years through contract problems and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to achieve expectations - maybe in what appears to be a last chance - under new promotional backing.
He opened tentatively, with the two boxers willing to overcommit in a tentative initial rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who utilized a tight guard to narrowly win the cleaner periods.
The spectators' acceptance decreased during regular grabbing, with the challenger falling to the floor several times during clinches.
Parker ended stronger, but many rounds were challenging to assess. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just one round.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to win the European light heavyweight title.
The venue became quiet for a deeply poignant tribute ahead of the contest as 10 bells rang in honor of Manchester's own Hatton, who died at age 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the last bell disappeared, the silence became a shout of "only one Hatton".
The fighting during the bout matched the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the chin in the second round, getting up unsteadily to his feet on the count of eight.
But the traditional red shorts of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was marked up early, noticeable damage developing under his eye as the duo landed powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur edged the verdict with judges scorecards of 114-114, close margin and clearer margin, but both fighters were relentless and courageous, exactly what their inspiration the legend embodied.
