British light heavyweight Buatsi earned a win yet disappointing beginning to life under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a competitive 10-round contest at the Manchester venue.
But Parker had his moments, delivering effective single shots in a match where the styles never quite clicked, with excessive holding disrupting the contest.
Two judges had it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," Buatsi commented in the ringside as he was met by boos from the spectators.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Several boxing experts thought the challenger, 31, merited the decision but the British boxer endured the second setback of his 28-fight career.
The Champion Secures Win in Slow Match
His career development has stalled in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what appears to be a last chance - under new promotional backing.
He began cautiously, with the two boxers willing to take risks in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who utilized a solid defense to barely take the cleaner periods.
The audience's tolerance decreased amid constant clinching, with Parker going down several times during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Hatton Tribute Motivates All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a excellent all-Manchester fight to win the European light-heavyweight championship.
The arena became quiet for a extremely emotional homage before the fight as 10 bells rang in remembrance of local hero Ricky Hatton, who passed away aged 46 in last month.
It was the first major televised boxing event in the city since the passing of Hatton. As the last bell ended, the silence gave way to a chant of "only one Ricky Hatton".
The action inside the ropes matched the feeling. The eventual winner was floored by a significant blow flush on the jaw in the initial stage, rising shakily to his footing on the count of eight.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in rival City blue - was injured quickly, heavy swelling forming under his eye as the pair traded hard punches.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the intensity seldom decreased over the full distance.
The victor barely secured the decision with judges scorecards of draw, close margin and 115-112, but the two athletes were determined and brave, everything their idol the legend embodied.
