UK 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 medal winner's work rate likely gained him a majority decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger found success, landing some telling individual punches in a fight where the techniques never quite clicked, with constant grabbing spoiling the fight.
Two judges judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my best performance but how do champions respond? They win," Buatsi commented in the ringside as he was met by negative reactions from the crowd.
The British fighter bounced back after his first professional defeat - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts believed Parker, thirty-one, deserved the victory but the British boxer experienced the second defeat of his 28-match career.
Buatsi Earns Win in Slow Encounter
His career development has plateaued in recent years through management issues and long spells of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to take risks in a cagey initial rounds.
The challenger, whose only previous defeat 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 halfway stage, the underdog had kept it close, causing problems for Buatsi, who utilized a protective stance to edge the more effective stanzas.
The audience's tolerance diminished during frequent holding, with Parker falling to the floor various instances during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor advances, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Hatton Memorial Motivates Local Rivalry Battle
In the secondary fight, Arthur defeated Rea by divided decision in a outstanding all-Manchester battle to secure the continental championship.
The arena became quiet for a deeply poignant homage ahead of the contest as 10 bells tolled in remembrance of Manchester's own Hatton, who passed away aged 46 in recently.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the last bell faded, the stillness gave way to a roar of "there's only one Hatton".
The fighting within the ring equaled the sentiment. Arthur was knocked down by a left hook squarely on the jaw in the initial stage, getting up unsteadily to his feet on the referee's count.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was marked up quickly, heavy swelling forming under his eye as the pair traded punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur edged the decision with scoring tallies of even score, narrow lead and 115-112, but the two athletes were determined and full of heart, exactly what their hero Hatton stood for.
