UK light heavyweight Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a judges' verdict in a competitive ten-round fight at the Co-op Live Arena.
But the challenger found success, landing some telling clean blows in a fight where the approaches failed to mesh, with constant grabbing spoiling the action.
The officials had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best display but what do champions do? They succeed," the victor commented in the arena as he was met by boos from the crowd.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Some ringside observers thought Parker, 31, should have been awarded the win but the Derbyshire fighter suffered the second defeat of his 28-match professional journey.
Buatsi Earns Win in Dull Encounter
His career development has plateaued in the past few years through contract problems and considerable time of lack of fights.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a tentative opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second bout at the higher weight class.
By the halfway stage, the underdog had kept it close, making life awkward for Buatsi, who worked behind a tight guard to edge the better stanzas.
The audience's tolerance diminished amid frequent holding, with Parker slipping to the canvas several times during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
The victor advances, but with the presence of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a excellent all-Manchester fight to secure the European light-heavyweight championship.
The arena grew hushed for a extremely emotional tribute ahead of the contest as 10 bells tolled in remembrance of the city's native Ricky Hatton, who passed away at age 46 in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the final chime disappeared, the stillness transitioned to a roar of "there's just one Hatton".
The action inside the ropes matched the sentiment. Arthur was floored by a powerful punch squarely on the face in the early round, rising shakily to his feet on the referee's count.
But the red-colored equipment of the fighter soon advanced again. On the opposite side, the opponent - in competitive blue - was marked up soon, significant bruising forming under his face as the duo landed hard punches.
The challenger, 27, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over twelve rounds.
Arthur edged the verdict with official scores of 114-114, narrow lead and clearer margin, but the two athletes were relentless and brave, exactly what their inspiration the legend represented.
