British light-heavyweight Buatsi made a winning yet unimpressive start to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight 10-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling single shots in a contest where the approaches never quite clicked, with frequent clinching disrupting the contest.
Two judges had it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," Buatsi said in the ring as he was met by negative reactions from the audience.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in February - to claim a 20th career victory.
Some ringside observers believed Parker, thirty-one, should have been awarded the decision but the contender endured the second loss of his 28-fight professional journey.
Buatsi Earns Triumph in Slow Affair
His career development has slowed in the past few years through management issues and extended periods of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to achieve expectations - perhaps in what appears to be a last chance - under fresh management.
He started carefully, with the two boxers willing to be aggressive in a calculated initial rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second fight at light heavyweight.
By the halfway stage, Parker had kept it close, causing problems for Buatsi, who utilized a tight guard to narrowly win the better rounds.
The audience's tolerance wore thin amid frequent holding, with Parker slipping to the canvas various instances during clinches.
Parker ended stronger, but several stanzas were hard to judge. Although, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Hatton Tribute Motivates All-Manchester Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by divided decision in a terrific local rivalry fight to capture the European light heavyweight championship.
The stadium became quiet for a extremely emotional memorial before the fight as 10 bells rang in memory of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the last bell disappeared, the stillness gave way to a shout of "there's only one Hatton".
The action inside the ropes matched the sentiment. The eventual winner was floored by a left hook directly to the face in the early round, rising shakily to his feet on the eight count.
But the Manchester United-red attire of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was damaged early, significant bruising appearing under his orbital area as the duo traded powerful shots.
Rea, 27, delivered effective strikes but the champion, 34, matched the intensity with stinging uppercuts as the action hardly diminished over 12 rounds.
Arthur barely secured the result with judges scorecards of 114-114, narrow lead and clearer margin, but each competitor were persistent and full of heart, all the qualities their idol the legend represented.
