British light-heavyweight Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a competitive 10-round bout at the Manchester venue.
But the challenger had his moments, landing some telling clean blows in a fight where the styles never quite clicked, with frequent clinching spoiling the contest.
The officials judged it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest showing but what defines champions? They succeed," the victor commented in the ring as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts felt Parker, thirty-one, merited the victory but the Derbyshire fighter experienced the second defeat of his 28-bout career.
The Champion Secures Victory in Slow Encounter
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with neither fighter prepared to take risks in a calculated early stages.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was making just his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a solid defense to barely take the cleaner rounds.
The spectators' acceptance diminished amid constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
Parker ended stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the secondary fight, Arthur beat Rea by split-decision in a outstanding all-Manchester battle to win the continental championship.
The arena became quiet for a extremely emotional tribute ahead of the contest as ten bells sounded in honor of the city's native Hatton, who passed away at age 46 in recently.
It was the premier televised match card in the urban center since Hatton's death. As the last bell disappeared, the quiet gave way to a chant of "only one Ricky Hatton".
The action inside the ropes reflected the emotion. Arthur was floored by a powerful punch squarely on the chin in the second round, rising shakily to his footing on the count of eight.
But the traditional red equipment of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up soon, noticeable damage developing under his orbital area as the fighters exchanged powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the action hardly diminished over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, close margin and wider gap, but both fighters were persistent and full of heart, exactly what their idol the legend embodied.
