British light heavyweight Buatsi secured a victory yet underwhelming start to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a split decision in a close ten-round bout at the Co-op Live Arena.
But Parker had his moments, connecting with powerful individual punches in a fight where the approaches didn't complement each other, with constant grabbing marring the action.
The officials had it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi said in the arena as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his initial pro loss - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Various analysts believed the challenger, thirty-one, merited the win but the British boxer endured the second loss of his 28-match professional journey.
The Champion Secures Triumph in Slow Match
Buatsi's progress has stalled in the past few years through management issues and considerable time of inactivity.
Once tipped as the next star of the British fight scene, he now finds himself trying to achieve expectations - possibly in what appears to be a last chance - under fresh management.
He began cautiously, with neither fighter prepared to take risks in a cagey early stages.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second bout at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who operated with a tight guard to edge the more effective periods.
The crowd's patience diminished amid frequent holding, with Parker going down multiple occasions during grappling.
The underdog ended stronger, but multiple periods were hard to judge. However, ex-champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, awarding Buatsi just one round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Arthur beat Rea by divided decision in a outstanding all-Manchester contest to win the European light-heavyweight belt.
The arena fell silent for a deeply poignant tribute before the fight as 10 bells tolled in memory of the city's native Hatton, who died at age 46 in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the last bell disappeared, the stillness gave way to a shout of "there's only one Hatton".
The competition during the bout matched the feeling. The eventual winner was floored by a left hook directly to the jaw in the initial stage, standing uncertainly to his footing on the referee's count.
But the Manchester United-red equipment of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, noticeable damage appearing under his orbital area as the duo traded hard punches.
Rea, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur barely secured the verdict with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were determined and full of heart, exactly what their inspiration Hatton stood for.
