UK light-heavyweight Buatsi made a winning yet unimpressive start to his career under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a tight ten-round contest at the boxing arena.
But Parker found success, connecting with powerful clean blows in a match where the styles failed to mesh, with excessive holding marring the contest.
The officials had it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my greatest display but what do champions do? They win," the victor commented in the ringside as he was met by disapproval from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Various analysts felt the challenger, thirty-one, should have been awarded the decision but the contender suffered the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Uneventful Affair
His career development has slowed in recent times through contract problems and extended periods of inactivity.
Once tipped as the future of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to take risks in a tentative initial rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was participating in his second fight at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who utilized a solid defense to barely take the cleaner rounds.
The audience's tolerance diminished amid regular grabbing, with the challenger slipping to the canvas various instances during clinches.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Russian star Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a terrific local rivalry fight to win the continental belt.
The stadium fell silent for a deeply poignant memorial ahead of the contest as 10 bells rang in remembrance of local hero Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast match card in the city since Hatton's passing. As the concluding sound ended, the quiet gave way to a shout of "there's just one Hatton".
The action inside the ropes equaled the sentiment. Arthur was knocked down by a significant blow flush on the face in the second round, rising shakily to his feet on the eight count.
But the red-colored equipment of the fighter soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up soon, significant bruising developing under his face as the pair traded hard punches.
Rea, 27, connected with strong blows but Arthur, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur narrowly won the result with judges scorecards of 114-114, narrow lead and clearer margin, but the two athletes were relentless and brave, exactly what their idol Hatton stood for.
