UK light heavyweight Buatsi earned a win yet disappointing start to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a competitive ten-round fight at the Co-op Live Arena.
But the challenger had his moments, delivering effective clean blows in a contest where the styles didn't complement each other, with constant grabbing marring the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my finest showing but what do champions do? They win," Buatsi said in the ringside as he was greeted with negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th pro success.
Some ringside observers thought Parker, 31, deserved the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Affair
His career development has slowed in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to achieve expectations - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with both competitors ready to be aggressive in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second fight at the higher weight class.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who operated with a solid defense to edge the cleaner periods.
The spectators' acceptance wore thin during frequent holding, with the challenger falling to the floor various instances during clinches.
Parker finished the stronger, but several stanzas were challenging to assess. However, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the co-main event, Lyndon Arthur beat Rea by divided decision in a outstanding all-Manchester battle to win the European light heavyweight belt.
The venue became quiet for a extremely emotional memorial prior to the bout as ten bells rang in honor of local hero Hatton, who passed away at age 46 in recently.
It was the premier televised fight night in the location since the passing of Hatton. As the last bell disappeared, the quiet gave way to a roar of "there's just one Hatton".
The action within the ring matched the emotion. The eventual winner was sent to the canvas by a left hook squarely on the chin in the second round, rising shakily to his position on the referee's count.
But the red-colored equipment of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was injured early, significant bruising developing under his orbital area as the pair traded hard punches.
Rea, 27, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the pace seldom decreased over the full distance.
The victor edged the verdict with official scores of 114-114, close margin and clearer margin, but both fighters were relentless and courageous, everything their hero Hatton embodied.
