UK light-heavyweight Buatsi made a winning yet disappointing start to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a majority decision in a close ten-round contest at the Manchester venue.
But Parker found success, delivering effective clean blows in a fight where the techniques didn't complement each other, with excessive holding disrupting the action.
The scoring judges judged it 96-94 to Buatsi, with the third a even score.
"It wasn't my greatest showing but what defines champions? They succeed," Buatsi said in the arena as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Some ringside observers believed Parker, thirty-one, deserved the win but the British boxer endured the second defeat of his 28-fight career.
Buatsi Earns Victory in Dull Affair
Buatsi's progress has stalled in recent years through promotional disputes and long spells of inactivity.
Previously predicted as the future of the British fight scene, he now stands trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with both competitors prepared to take risks in a tentative 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 competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who utilized a solid defense to narrowly win the better stanzas.
The crowd's patience decreased because of frequent holding, with the challenger going down various instances during clinches.
Parker finished the stronger, but multiple periods were hard to judge. Although, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific local rivalry battle to secure the European light heavyweight belt.
The stadium grew hushed for a deeply poignant memorial ahead of the contest as ten bells tolled in memory of Manchester's own Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast fight night in the city since Hatton's passing. As the concluding sound ended, the quiet gave way to a shout of "there's just one Ricky Hatton".
The competition within the ring equaled the sentiment. Arthur was sent to the canvas by a left hook squarely on the jaw in the second round, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was damaged quickly, significant bruising developing under his eye as the pair landed powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor edged the result with scoring tallies of even score, close margin and clearer margin, but the two athletes were relentless and courageous, everything their inspiration the legend represented.
