British light-heavyweight Buatsi earned a win yet underwhelming debut to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight ten-round contest at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a fight where the approaches failed to mesh, with frequent clinching spoiling the action.
The officials scored it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best showing but what do champions do? They succeed," Buatsi stated in the ring as he was met by negative reactions from the crowd.
The British fighter got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th career victory.
Several boxing experts thought the challenger, 31, merited the win but the British boxer endured the second defeat of his 28-match career.
The Champion Claims Victory in Uneventful Affair
His career development has plateaued in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now is positioned trying to achieve expectations - maybe in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter ready to be aggressive in a cagey initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who worked behind a tight guard to narrowly win the better periods.
The audience's tolerance decreased during frequent holding, with Parker slipping to the canvas several times during grappling.
Parker ended stronger, but many rounds were hard to judge. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Hatton Homage Fuels Local Rivalry Fight
In the co-main event, Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester fight to win the continental title.
The stadium grew hushed for a extremely emotional homage before the fight as 10 bells sounded in honor of Manchester's own Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised match card in the location since Hatton's passing. As the last bell disappeared, the quiet transitioned to a roar of "there's just one Hatton".
The competition within the ring reflected the feeling. The eventual winner was floored by a left hook squarely on the jaw in the second round, rising shakily to his position on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in competitive blue - was marked up soon, significant bruising developing under his eye as the fighters landed powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over the full distance.
Arthur barely secured the result with official scores of even score, close margin and 115-112, but each competitor were relentless and courageous, everything their idol the legend stood for.
