UK light heavyweight Buatsi made a winning yet disappointing start to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight ten-round fight at the Manchester venue.
But the challenger landed significant shots, connecting with powerful clean blows in a contest where the styles failed to mesh, with frequent clinching marring the fight.
The scoring judges judged it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my best showing but what do champions do? They succeed," Buatsi said in the arena as he was greeted with negative reactions from the crowd.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Some ringside observers thought the challenger, thirty-one, deserved the win but the British boxer experienced the second loss of his 28-bout professional journey.
Buatsi Claims Victory in Slow Match
His career development has plateaued in recent years through management issues and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - possibly in what seems like a final roll of the dice - under recent support.
He began cautiously, with both competitors prepared to be aggressive in a calculated early stages.
The challenger, whose single earlier setback 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 the higher weight class.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who operated with a tight guard to edge the better stanzas.
The crowd's patience decreased amid constant clinching, with Parker going down multiple occasions during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. Although, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just one round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian star Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Tribute Inspires Manchester Derby Battle
In the co-main event, Lyndon Arthur beat Bradley Rea by divided decision in a excellent all-Manchester fight to capture the European light-heavyweight belt.
The arena grew hushed for a profoundly moving homage prior to the bout as a bell ceremony rang in honor of Manchester's own Ricky Hatton, who died 46 years old in September.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound disappeared, the quiet gave way to a shout of "only one Ricky Hatton".
The competition within the ring matched the sentiment. The eventual winner was floored by a left hook squarely on the face in the second round, rising shakily to his position on the count of eight.
But the Manchester United-red shorts of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was damaged soon, noticeable damage developing under his orbital area as the fighters exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over the full distance.
Arthur edged the result with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were relentless and full of heart, exactly what their idol Hatton embodied.
