UK light heavyweight Buatsi earned a win yet unimpressive beginning to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a competitive ten-round contest at the Co-op Live Arena.
But Parker had his moments, landing some telling individual punches in a contest where the techniques didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi said in the ringside as he was faced boos from the spectators.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Some ringside observers felt the challenger, 31, merited the win but the contender suffered the second setback of his 28-match career.
The Champion Secures Triumph in Dull Affair
The fighter's advancement has slowed in recent years through contract problems and extended periods of inactivity.
Previously predicted as the future of the British fight scene, he now stands trying to achieve expectations - perhaps in what feels like a final roll of the dice - under recent support.
He began cautiously, with both competitors prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was competing in only his second appearance at light heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who operated with a protective stance to barely take the cleaner periods.
The audience's tolerance diminished amid constant clinching, with Parker falling to the floor multiple occasions during grappling.
The underdog closed well, but many rounds were hard to judge. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still seems difficult.
Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester battle to win the continental belt.
The arena became quiet for a profoundly moving memorial ahead of the contest as ten bells tolled in honor of Manchester's own Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound disappeared, the stillness transitioned to a chant of "only one Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the jaw in the second round, standing uncertainly to his footing on the eight count.
But the traditional red shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in opposing blue - was damaged soon, noticeable damage forming under his orbital area as the fighters traded punishing blows.
The challenger, 27, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the intensity hardly diminished over 12 rounds.
The victor edged the decision with official scores of draw, 115-113 and clearer margin, but the two athletes were relentless and courageous, everything their idol Hatton embodied.
