UK light-heavyweight Joshua Buatsi made a winning yet unimpressive beginning to life under new promoters with a points victory over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close ten-round fight at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a match where the styles didn't complement each other, with excessive holding disrupting the fight.
The scoring judges had it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best showing but how do champions respond? They succeed," the victor stated in the ringside as he was faced disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Some ringside observers thought Parker, 31, merited the win but the British boxer experienced the second setback of his 28-bout career.
The Champion Earns Triumph in Slow Match
His career development has slowed in recent years through management issues and long spells of lack of fights.
Once tipped as the next star of British boxing, he now stands trying to realize his potential - perhaps in what appears to be a last chance - under fresh management.
He began cautiously, with the two boxers willing to take risks in a tentative initial rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second appearance at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to edge the cleaner periods.
The spectators' acceptance wore thin during frequent holding, with Parker slipping to the canvas various instances during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just a single round.
Buatsi advances, but with the likes of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the co-main event, Arthur beat Bradley Rea by divided decision in a terrific local rivalry contest to secure the European light-heavyweight championship.
The arena became quiet for a deeply poignant homage before the fight as a bell ceremony sounded in remembrance of the city's native Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised boxing event in the city since Hatton's death. As the final chime ended, the quiet became a shout of "there's just one Ricky Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was floored by a left hook flush on the chin in the second round, standing uncertainly to his position on the eight count.
But the traditional red equipment of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was injured quickly, heavy swelling developing under his eye as the fighters traded punishing blows.
Rea, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the action rarely dropped over 12 rounds.
The victor narrowly won the verdict with official scores of 114-114, narrow lead and 115-112, but the two athletes were determined and brave, everything their inspiration Hatton represented.
