UK light-heavyweight Buatsi made a winning yet underwhelming debut to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a tight 10-round bout at the Co-op Live Arena.
But the challenger found success, landing some telling clean blows in a match where the styles failed to mesh, with frequent clinching disrupting the action.
The officials had it 96-94 to the winner, with the third a 95-95.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi commented in the arena as he was faced disapproval from the audience.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts thought the challenger, thirty-one, merited the victory but the British boxer endured the second defeat of his 28-bout career.
The Champion Earns Triumph in Slow Match
The fighter's advancement has stalled in recent years through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors willing to take risks in a calculated opening few 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 bout at the higher weight class.
By the middle rounds, the underdog had stayed in contention, making life awkward for the favorite, who operated with a protective stance to barely take the more effective rounds.
The spectators' acceptance diminished during constant clinching, with Parker slipping to the canvas several times during grappling.
Parker closed well, but several stanzas were difficult to score. Although, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just one round.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Hatton Memorial Fuels All-Manchester Fight
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a terrific all-Manchester battle to win the continental championship.
The arena grew hushed for a extremely emotional homage prior to the bout as 10 bells rang in remembrance of local hero Hatton, who passed away 46 years old in recently.
It was the first major televised match card in the urban center since Hatton's passing. As the last bell disappeared, the stillness gave way to a shout of "only one Hatton".
The competition within the ring reflected the emotion. The eventual winner was sent to the canvas by a powerful punch directly to the jaw in the second round, getting up unsteadily to his position on the count of eight.
But the traditional red attire of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged soon, noticeable damage forming under his face as the pair traded powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, responded in kind with powerful upward punches as the pace rarely dropped over 12 rounds.
The victor narrowly won the decision with judges scorecards of draw, 115-113 and wider gap, but both fighters were determined and full of heart, exactly what their idol the legend stood for.
