UK light-heavyweight Buatsi made a winning yet underwhelming debut to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a majority decision in a tight 10-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling individual punches in a contest where the approaches didn't complement each other, with constant grabbing disrupting the action.
The officials scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my finest performance but what do champions do? They win," Buatsi said in the ringside as he was met by boos from the audience.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers felt Parker, 31, merited the win but the British boxer endured the second loss of his 28-match career.
Buatsi's progress has stalled in recent years through promotional disputes and considerable time of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to realize his potential - maybe in what feels like a last chance - under fresh management.
He opened tentatively, with neither fighter willing to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was making just his second bout at light heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who operated with a tight guard to edge the cleaner stanzas.
The spectators' acceptance diminished amid regular grabbing, with Parker going down several times during grappling.
Parker closed well, but many rounds were challenging to assess. Although, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
The victor progresses, but with the likes of power puncher David Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
In the co-main event, Lyndon Arthur overcame Bradley Rea by split-decision in a outstanding Manchester vs Manchester battle to secure the European light heavyweight title.
The arena became quiet for a deeply poignant memorial ahead of the contest as ten bells rang in memory of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the premier televised match card in the urban center since the passing of Hatton. As the concluding sound disappeared, the quiet gave way to a roar of "there's just one Hatton".
The fighting during the bout matched the emotion. Arthur was sent to the canvas by a left hook flush on the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the traditional red attire of Arthur soon came forward again. Across the ring, the opponent - in competitive blue - was damaged quickly, heavy swelling appearing under his face as the fighters exchanged hard punches.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur edged the verdict with official scores of draw, narrow lead and 115-112, but each competitor were persistent and full of heart, everything their hero the legend stood for.
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