UK light heavyweight Buatsi secured a victory yet underwhelming debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a competitive 10-round fight at the Co-op Live Arena.
But the challenger had his moments, delivering effective single shots in a contest where the techniques never quite clicked, with frequent clinching spoiling the contest.
The officials judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my best display but what do champions do? They prevail," the victor commented in the ring as he was greeted with disapproval from the spectators.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a 20th career victory.
Some ringside observers believed Parker, 31, should have been awarded the victory but the British boxer suffered the second setback of his 28-fight professional journey.
The Champion Secures Win in Uneventful Match
His career development has stalled in recent times through contract problems and considerable time of lack of fights.
Once tipped as the rising talent of British boxing, he now finds himself trying to realize his potential - maybe in what feels like a final roll of the dice - under fresh management.
He started carefully, with both competitors willing to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second bout at light heavyweight.
By the middle rounds, Parker had kept it close, causing problems for Buatsi, who utilized a tight guard to narrowly win the cleaner stanzas.
The spectators' acceptance decreased amid regular grabbing, with the challenger falling to the floor several times during grappling.
The underdog closed well, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Tribute Fuels All-Manchester Fight
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry contest to win the European light heavyweight championship.
The venue became quiet for a profoundly moving memorial prior to the bout as ten bells tolled in honor of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the first major televised fight night in the city since Hatton's passing. As the last bell ended, the silence transitioned to a roar of "there's just one Hatton".
The action within the ring reflected the emotion. Arthur was knocked down by a powerful punch directly to the chin in the early round, getting up unsteadily to his feet on the eight count.
But the red-colored equipment of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was injured soon, significant bruising developing under his eye as the fighters landed powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the pace seldom decreased over the full distance.
Arthur edged the result with scoring tallies of even score, close margin and 115-112, but each competitor were determined and brave, all the qualities their hero the legend stood for.
