UK light heavyweight Buatsi earned a win yet disappointing beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a close 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, landing some telling clean blows in a contest where the approaches never quite clicked, with excessive holding spoiling the fight.
The scoring judges scored it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest performance but what do champions do? They prevail," the victor commented in the ringside as he was met by boos from the spectators.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Various analysts thought the challenger, thirty-one, deserved the decision but the British boxer experienced the second setback of his 28-fight professional journey.
His career development has slowed in recent times through management issues and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to realize his potential - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with both competitors willing to be aggressive in a cagey initial rounds.
The challenger, 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 fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who utilized a tight guard to narrowly win the cleaner stanzas.
The spectators' acceptance decreased amid frequent holding, with the challenger going down several times during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
In the secondary fight, Lyndon Arthur defeated Bradley Rea by split-decision in a outstanding Manchester vs Manchester battle to win the European light heavyweight title.
The arena fell silent for a extremely emotional tribute before the fight as ten bells rang in remembrance of the city's native Hatton, who died at age 46 in recently.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the final chime ended, the stillness gave way to a roar of "only one Ricky Hatton".
The action within the ring matched the sentiment. Arthur was floored by a powerful punch squarely on the chin in the early round, rising shakily to his feet on the count of eight.
But the red-colored equipment of the fighter soon came forward again. Across the ring, the opponent - in rival City blue - was marked up early, heavy swelling developing under his eye as the fighters exchanged powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the action hardly diminished over twelve rounds.
The victor edged the result with official scores of even score, narrow lead and 115-112, but each competitor were persistent and courageous, all the qualities their idol Hatton represented.
Eva de Vries is a passionate book lover and local writer from Eindhoven.
