British light heavyweight Joshua Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive 10-round fight at the Co-op Live Arena.
But Parker found success, delivering effective clean blows in a match where the styles didn't complement each other, with frequent clinching spoiling the action.
Two judges judged it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest performance but how do champions respond? They prevail," Buatsi said in the ring as he was faced negative reactions from the audience.
The British fighter 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 the challenger, thirty-one, deserved the victory but the Derbyshire fighter experienced the second defeat of his 28-fight professional journey.
Buatsi Claims Win in Slow Encounter
His career development has slowed in recent years through contract problems and considerable time of lack of fights.
Once tipped as the future of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers prepared to overcommit in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was making just his second appearance at light heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who utilized a solid defense to barely take the more effective rounds.
The spectators' acceptance diminished because of regular grabbing, with the challenger falling to the floor various instances during close exchanges.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the co-main event, Lyndon Arthur beat Rea by split-decision in a excellent local rivalry battle to secure the European light-heavyweight championship.
The venue became quiet for a deeply poignant memorial prior to the bout as ten bells tolled in honor of local hero Hatton, who succumbed at age 46 in September.
It was the first major televised match card in the urban center since Hatton's death. As the last bell disappeared, the quiet gave way to a shout of "only one Hatton".
The fighting within the ring equaled the sentiment. Arthur was knocked down by a left hook squarely on the chin in the second round, rising shakily to his feet on the count of eight.
But the red-colored attire of Arthur soon came forward again. From the other corner, the opponent - in rival City blue - was marked up quickly, noticeable damage developing under his face as the duo landed punishing blows.
The challenger, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor narrowly won the verdict with judges scorecards of even score, close margin and 115-112, but each competitor were determined and courageous, exactly what their hero Hatton embodied.
