British light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a close 10-round contest at the boxing arena.
But Parker landed significant shots, connecting with powerful individual punches in a contest where the techniques failed to mesh, with frequent clinching marring the action.
Two judges had it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest display but what do champions do? They prevail," Buatsi commented in the arena as he was faced negative reactions from the crowd.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Several boxing experts felt the challenger, thirty-one, merited the victory but the Derbyshire fighter endured the second setback of his 28-match professional journey.
The Champion Earns Triumph in Uneventful Encounter
His career development has plateaued in the past few years through management issues and considerable time of lack of fights.
Once tipped as the future of the British fight scene, he now finds himself trying to realize his potential - maybe in what feels like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers willing to overcommit in a cagey initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a protective stance to edge the cleaner periods.
The audience's tolerance wore thin because of frequent holding, with the challenger slipping to the canvas several times during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Inspires Manchester Derby Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to capture the European light heavyweight title.
The stadium fell silent for a extremely emotional memorial ahead of the contest as 10 bells rang in memory of local hero Hatton, who succumbed aged 46 in recently.
It was the premier televised match card in the urban center since Hatton's passing. As the concluding sound disappeared, the silence became a roar of "there's just one Ricky Hatton".
The fighting within the ring reflected the feeling. Arthur was sent to the canvas by a significant blow squarely on the chin in the early round, rising shakily to his feet on the count of eight.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was injured early, significant bruising appearing under his eye as the pair landed hard punches.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with powerful upward punches as the action rarely dropped over the full distance.
Arthur barely secured the decision with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were determined and brave, exactly what their inspiration the legend represented.
