UK light-heavyweight Buatsi earned a win yet unimpressive start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a competitive ten-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling clean blows in a contest where the techniques didn't complement each other, with constant grabbing marring the fight.
The scoring judges had it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest performance but what do champions do? They prevail," the victor commented in the arena as he was met by boos from the crowd.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers believed Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter endured the second loss of his 28-match career.
Buatsi Secures Win in Slow Match
The fighter's advancement has slowed in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what appears to be a last chance - under recent support.
He started carefully, with the two boxers ready to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was making just his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, causing problems for the favorite, who utilized a tight guard to narrowly win the better periods.
The crowd's patience diminished because of frequent holding, with Parker going down various instances during grappling.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
The victor advances, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Contest
In the secondary fight, Arthur beat Rea by divided decision in a outstanding all-Manchester fight to win the European light heavyweight belt.
The stadium became quiet for a deeply poignant tribute prior to the bout as 10 bells tolled in remembrance of local hero Hatton, who died aged 46 in last month.
It was the initial significant broadcast fight night in the location since the passing of Hatton. As the concluding sound disappeared, the quiet gave way to a chant of "there's only one Ricky Hatton".
The competition inside the ropes reflected the emotion. Arthur was knocked down by a powerful punch directly to the jaw in the initial stage, rising shakily to his position on the eight count.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was marked up soon, noticeable damage forming under his orbital area as the duo landed punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over the full distance.
Arthur narrowly won the verdict with scoring tallies of 114-114, close margin and clearer margin, but the two athletes were relentless and full of heart, all the qualities their idol Hatton embodied.
