UK light heavyweight Buatsi made a winning yet disappointing start to life under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger had his moments, delivering effective clean blows in a match where the approaches never quite clicked, with excessive holding marring the action.
Two judges had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest display but what do champions do? They succeed," Buatsi stated in the arena as he was greeted with disapproval from the crowd.
The Londoner bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Various analysts thought the challenger, 31, should have been awarded the win but the British boxer experienced the second setback of his 28-bout career.
Buatsi Earns Victory in Slow Encounter
Buatsi's progress has stalled in the past few years through contract problems and long spells of lack of fights.
Once tipped as the next star of the British fight scene, he now finds himself trying to achieve expectations - perhaps in what seems like a final roll of the dice - under fresh management.
He started carefully, with both competitors ready to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was participating in his second appearance at the higher weight class.
By the fight's midpoint, Parker had kept it close, making life awkward for Buatsi, who utilized a protective stance to narrowly win the better rounds.
The spectators' acceptance diminished during constant clinching, with Parker slipping to the canvas various instances during clinches.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just one round.
The victor advances, but with the caliber of hard hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a excellent all-Manchester contest to capture the European light heavyweight belt.
The arena became quiet for a extremely emotional homage prior to the bout as a bell ceremony rang in memory of the city's native Ricky Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the final chime ended, the quiet gave way to a chant of "there's just one Ricky Hatton".
The competition inside the ropes equaled the sentiment. Arthur was knocked down by a significant blow squarely on the chin in the second round, rising shakily to his feet on the count of eight.
But the traditional red shorts of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up early, noticeable damage forming under his eye as the fighters exchanged hard punches.
Rea, twenty-seven, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the intensity seldom decreased over the full distance.
The victor barely secured the verdict with scoring tallies of draw, close margin and 115-112, but both fighters were determined and full of heart, exactly what their inspiration the legend embodied.
