British light-heavyweight Buatsi secured a victory yet disappointing debut to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a close 10-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective individual punches in a fight where the techniques failed to mesh, with frequent clinching marring the contest.
Two judges judged it 96-94 to the winner, with the final judge a even score.
"It wasn't my finest performance but what do champions do? They prevail," the victor commented in the ring as he was met by disapproval from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with his previous opponent in last winter - to secure a 20th pro success.
Some ringside observers felt the challenger, thirty-one, merited the win but the contender experienced the second loss of his 28-bout professional journey.
The Champion Secures Triumph in Dull Match
His career development has slowed in recent times through management issues and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now finds himself trying to realize his potential - perhaps in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with both competitors ready to take risks in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second appearance at light-heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for Buatsi, who worked behind a tight guard to narrowly win the better periods.
The spectators' acceptance decreased because of regular grabbing, with the challenger slipping to the canvas various instances during grappling.
The underdog closed well, but many rounds were hard to judge. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Motivates All-Manchester Contest
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to capture the continental belt.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as ten bells rang in honor of local hero Hatton, who passed away aged 46 in September.
It was the first major televised boxing event in the city since Hatton's death. As the concluding sound ended, the quiet gave way to a chant of "there's only one Ricky Hatton".
The fighting inside the ropes matched the feeling. Arthur was floored by a powerful punch flush on the face in the early round, standing uncertainly to his feet on the eight count.
But the traditional red shorts of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged early, noticeable damage forming under his orbital area as the fighters landed hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with stinging uppercuts as the action hardly diminished over 12 rounds.
Arthur narrowly won the verdict with scoring tallies of even score, 115-113 and clearer margin, but each competitor were persistent and full of heart, everything their inspiration Hatton represented.
