British light heavyweight Joshua Buatsi secured a victory yet disappointing start to his career under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a close 10-round bout at the boxing arena.
But Parker had his moments, delivering effective individual punches in a fight where the approaches didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," the victor stated in the ring as he was faced disapproval from the spectators.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers felt Parker, thirty-one, deserved the win but the contender experienced the second loss of his 28-match professional journey.
Buatsi Secures Win in Uneventful Encounter
The fighter's advancement has slowed in the past few years through contract problems and considerable time of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with the two boxers prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who worked behind a protective stance to barely take the more effective stanzas.
The audience's tolerance wore thin during frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
Parker closed well, but several stanzas were hard to judge. However, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the likes of power puncher Benavidez, and Russian champion Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels Manchester Derby Battle
In the co-main event, Arthur defeated Rea by close verdict in a terrific local rivalry contest to capture the European light-heavyweight championship.
The venue became quiet for a profoundly moving memorial prior to the bout as ten bells sounded in remembrance of the city's native Ricky Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast match card in the location since Hatton's passing. As the concluding sound disappeared, the quiet became a shout of "there's only one Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the jaw in the second round, rising shakily to his feet on the count of eight.
But the Manchester United-red equipment of the fighter soon came forward again. Across the ring, Rea - in rival City blue - was damaged soon, significant bruising appearing under his eye as the duo traded powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor edged the verdict with official scores of 114-114, close margin and 115-112, but the two athletes were persistent and full of heart, everything their hero Hatton stood for.
