UK light heavyweight Buatsi earned a win yet disappointing beginning to life under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a close ten-round contest at the Manchester venue.
But Parker landed significant shots, delivering effective clean blows in a contest where the styles failed to mesh, with excessive holding spoiling the action.
The scoring judges had it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best display but what defines champions? They prevail," Buatsi commented in the arena as he was greeted with boos from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts felt the challenger, 31, deserved the win but the Derbyshire fighter endured the second setback of his 28-match professional journey.
The Champion Earns Win in Slow Affair
His career development has slowed in the past few years through management issues and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - maybe in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter willing to be aggressive in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was making just his second appearance at the higher weight class.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who operated with a protective stance to edge the more effective stanzas.
The crowd's patience wore thin amid regular grabbing, with Parker going down multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. However, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher Benavidez, and Russian star Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Memorial Motivates Manchester Derby Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry battle to secure the European light heavyweight title.
The arena became quiet for a extremely emotional homage ahead of the contest as 10 bells sounded in remembrance of local hero Hatton, who passed away aged 46 in recently.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound faded, the stillness gave way to a shout of "only one Ricky Hatton".
The fighting during the bout reflected the feeling. The eventual winner was sent to the canvas by a powerful punch directly to the jaw in the second round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was marked up early, significant bruising forming under his eye as the fighters traded powerful shots.
Rea, 27, connected with strong blows but Arthur, 34, responded in kind with powerful upward punches as the intensity rarely dropped over twelve rounds.
The victor edged the decision with official scores of 114-114, narrow lead and clearer margin, but each competitor were relentless and full of heart, all the qualities their idol Hatton represented.
