UK light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a competitive 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective single shots in a match where the approaches never quite clicked, with frequent clinching spoiling the contest.
The officials judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but how do champions respond? They win," Buatsi said in the arena as he was faced negative reactions from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers believed Parker, 31, deserved the decision but the Derbyshire fighter experienced the second setback of his 28-bout professional journey.
Buatsi Earns Win in Dull Affair
His career development has stalled in recent times through management issues and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to take risks in a cagey opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after damaging his hand during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who operated with a tight guard to edge the better periods.
The spectators' acceptance decreased during regular grabbing, with Parker going down various instances during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. However, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Hatton Memorial Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a outstanding local rivalry fight to secure the continental championship.
The stadium became quiet for a profoundly moving homage before the fight as 10 bells rang in honor of the city's native Ricky Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the final chime ended, the stillness transitioned to a shout of "there's just one Ricky Hatton".
The competition within the ring equaled the feeling. Arthur was sent to the canvas by a significant blow squarely on the face in the initial stage, standing uncertainly to his position on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. On the opposite side, the opponent - in opposing blue - was damaged early, significant bruising forming under his orbital area as the fighters traded powerful shots.
The challenger, 27, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor narrowly won the result with scoring tallies of even score, 115-113 and 115-112, but the two athletes were determined and courageous, exactly what their inspiration Hatton represented.
