British light heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a tight 10-round fight at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a match where the techniques never quite clicked, with excessive holding marring the contest.
The scoring judges had it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest display but how do champions respond? They win," Buatsi commented in the ring as he was faced negative reactions from the audience.
The Londoner bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to secure a 20th pro success.
Various analysts felt Parker, 31, deserved the win but the contender experienced the second loss of his 28-bout career.
The Champion Claims Victory in Uneventful Match
Buatsi's progress has stalled in recent times through management issues and considerable time of inactivity.
Previously predicted as the next star of the British fight scene, he now stands trying to fulfil that early promise - maybe in what seems like a final roll of the dice - under recent support.
He began cautiously, with the two boxers prepared to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was participating in his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who utilized a protective stance to edge the better rounds.
The spectators' acceptance diminished during frequent holding, with the challenger slipping to the canvas several times during close exchanges.
Parker closed well, but many rounds were challenging to assess. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels All-Manchester Contest
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a terrific all-Manchester fight to secure the continental title.
The arena became quiet for a deeply poignant homage ahead of the contest as 10 bells rang in remembrance of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast match card in the city since Hatton's death. As the final chime ended, the quiet transitioned to a chant of "there's just one Ricky Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the chin in the initial stage, rising shakily to his position on the eight count.
But the traditional red equipment of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was marked up early, heavy swelling appearing under his orbital area as the fighters exchanged hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over 12 rounds.
Arthur narrowly won the verdict with judges scorecards of draw, 115-113 and wider gap, but the two athletes were persistent and brave, exactly what their inspiration the legend represented.
