UK light heavyweight Buatsi made a winning yet disappointing beginning to his career under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a tight 10-round fight at the boxing arena.
But Parker found success, delivering effective single shots in a match where the techniques never quite clicked, with frequent clinching spoiling the action.
The officials scored it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the ringside as he was faced disapproval from the crowd.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers believed the challenger, 31, should have been awarded the decision but the Derbyshire fighter suffered the second setback of his 28-fight career.
The Champion Claims Triumph in Dull Encounter
Buatsi's progress has slowed in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now is positioned trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with both competitors ready to be aggressive in a calculated opening few rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who utilized a protective stance to barely take the cleaner stanzas.
The audience's tolerance wore thin amid frequent holding, with the challenger going down various instances during clinches.
Parker closed well, but multiple periods were hard to judge. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent local rivalry contest to secure the continental belt.
The venue became quiet for a profoundly moving homage before the fight as 10 bells sounded in remembrance of local hero Ricky Hatton, who passed away at age 46 in September.
It was the premier televised fight night in the location since Hatton's passing. As the last bell faded, the stillness transitioned to a roar of "only one Hatton".
The fighting within the ring reflected the feeling. Arthur was sent to the canvas by a powerful punch flush on the face in the second round, rising shakily to his position on the eight count.
But the Manchester United-red attire of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was marked up soon, heavy swelling developing under his face as the pair traded hard punches.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the pace hardly diminished over 12 rounds.
The victor edged the decision with judges scorecards of 114-114, close margin and clearer margin, but each competitor were relentless and brave, exactly what their hero Hatton represented.
