British light-heavyweight Buatsi made a winning yet disappointing start to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a close 10-round contest at the boxing arena.
But Parker landed significant shots, connecting with powerful single shots in a match where the styles didn't complement each other, with frequent clinching spoiling the contest.
The officials judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what defines champions? They prevail," Buatsi commented in the ringside as he was greeted with boos from the audience.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts felt Parker, thirty-one, should have been awarded the decision but the contender experienced the second setback of his 28-match professional journey.
Buatsi Claims Triumph in Uneventful Encounter
Buatsi's progress has slowed in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers prepared to be aggressive in a cagey initial rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand in the contest, was participating in his second bout at the higher weight class.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who utilized a tight guard to edge the cleaner periods.
The spectators' acceptance diminished amid frequent holding, with Parker going down several times during close exchanges.
The underdog finished the stronger, but multiple periods were hard to judge. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Motivates Manchester Derby Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a outstanding local rivalry battle to secure the continental belt.
The venue became quiet for a extremely emotional memorial ahead of the contest as 10 bells tolled in memory of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the first major televised boxing event in the city since Hatton's passing. As the final chime disappeared, the stillness gave way to a chant of "there's only one Hatton".
The fighting inside the ropes equaled the feeling. The eventual winner was knocked down by a left hook squarely on the face in the early round, standing uncertainly to his position on the eight count.
But the red-colored attire of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was marked up soon, significant bruising developing under his face as the fighters exchanged punishing blows.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur barely secured the decision with scoring tallies of 114-114, 115-113 and clearer margin, but the two athletes were determined and courageous, exactly what their hero the legend stood for.
