British light-heavyweight Buatsi made a winning yet disappointing debut to his career under recent management with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a tight ten-round bout at the Manchester venue.
But Parker found success, delivering effective single shots in a match where the approaches failed to mesh, with constant grabbing marring the action.
The officials had it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi said in the arena as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers thought Parker, thirty-one, deserved the victory but the British boxer suffered the second setback of his 28-match career.
Buatsi Earns Win in Uneventful Match
The fighter's advancement has slowed in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to achieve expectations - maybe in what appears to be a final roll of the dice - under recent support.
He began cautiously, with the two boxers willing to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, causing problems for Buatsi, who worked behind a protective stance to barely take the more effective periods.
The crowd's patience wore thin amid regular grabbing, with Parker going down several times during close exchanges.
Parker ended stronger, but many rounds were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian star Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Memorial Fuels All-Manchester Contest
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester contest to secure the continental championship.
The stadium grew hushed for a deeply poignant homage ahead of the contest as 10 bells sounded in memory of Manchester's own Ricky Hatton, who died 46 years old in last month.
It was the premier televised match card in the city since Hatton's passing. As the concluding sound disappeared, the silence became a chant of "there's only one Ricky Hatton".
The competition during the bout equaled the sentiment. Arthur was knocked down by a powerful punch directly to the chin in the second round, rising shakily to his feet on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was marked up early, heavy swelling forming under his orbital area as the fighters exchanged punishing blows.
Rea, 27, landed power punches but Arthur, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur edged the verdict with official scores of even score, 115-113 and 115-112, but both fighters were determined and courageous, all the qualities their hero Hatton embodied.
