British light-heavyweight Buatsi secured a victory yet disappointing start to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a close ten-round fight at the Co-op Live Arena.
But Parker had his moments, landing some telling individual punches in a fight where the techniques never quite clicked, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my best display but what do champions do? They win," the victor commented in the arena as he was greeted with boos from the spectators.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Some ringside observers felt Parker, 31, merited the victory but the Derbyshire fighter suffered the second defeat of his 28-match professional journey.
The Champion Claims Triumph in Slow Affair
The fighter's advancement has slowed in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the next star of British boxing, he now stands trying to achieve expectations - possibly in what feels like a last chance - under fresh management.
He started carefully, with both competitors prepared to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for the favorite, who utilized a protective stance to edge the cleaner rounds.
The spectators' acceptance diminished because of regular grabbing, with the challenger falling to the floor multiple occasions during clinches.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the presence of hard hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires Manchester Derby Fight
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a excellent local rivalry contest to win the European light heavyweight belt.
The stadium became quiet for a profoundly moving tribute ahead of the contest as 10 bells rang in memory of local hero Hatton, who died 46 years old in September.
It was the first major televised match card in the city since the passing of Hatton. As the last bell disappeared, the silence became a roar of "there's just one Ricky Hatton".
The fighting within the ring reflected the feeling. Arthur was sent to the canvas by a left hook squarely on the jaw in the initial stage, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was damaged early, noticeable damage developing under his eye as the pair traded powerful shots.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the action hardly diminished over twelve rounds.
The victor narrowly won the verdict with judges scorecards of draw, narrow lead and clearer margin, but the two athletes were determined and courageous, all the qualities their idol Hatton embodied.
