UK light heavyweight Buatsi earned a win yet unimpressive start to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a tight ten-round bout at the boxing arena.
But the challenger landed significant shots, landing some telling clean blows in a match where the approaches didn't complement each other, with frequent clinching spoiling the action.
Two judges judged it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what defines champions? They prevail," the victor commented in the ringside as he was met by negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to earn a twentieth professional win.
Some ringside observers felt the challenger, 31, should have been awarded the win but the contender endured the second setback of his 28-bout career.
The Champion Earns Triumph in Uneventful Affair
Buatsi's progress has slowed in recent times through management issues and extended periods of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to overcommit in a tentative initial rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was competing in only his second bout at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who operated with a tight guard to edge the cleaner rounds.
The audience's tolerance diminished because of constant clinching, with the challenger slipping to the canvas several times during clinches.
The underdog closed well, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the secondary fight, Arthur overcame Rea by close verdict in a terrific all-Manchester fight to win the European light-heavyweight title.
The arena fell silent for a extremely emotional tribute prior to the bout as 10 bells tolled in remembrance of the city's native Ricky Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast fight night in the location since the passing of Hatton. As the last bell ended, the quiet gave way to a shout of "only one Hatton".
The fighting within the ring equaled the feeling. Arthur was floored by a powerful punch directly to the chin in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red attire of the fighter soon came forward again. Across the ring, Rea - in competitive blue - was marked up early, heavy swelling appearing under his orbital area as the fighters traded hard punches.
The challenger, 27, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace rarely dropped over twelve rounds.
Arthur edged the result with judges scorecards of 114-114, close margin and wider gap, but each competitor were determined and courageous, all the qualities their hero the legend embodied.
