UK light-heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a competitive ten-round fight at the boxing arena.
But Parker found success, delivering effective clean blows in a match where the techniques didn't complement each other, with excessive holding spoiling the action.
Two judges judged it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my greatest display but what do champions do? They succeed," the victor commented in the arena as he was faced boos from the crowd.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in February - to claim a 20th pro success.
Various analysts felt the challenger, 31, deserved the victory but the British boxer suffered the second loss of his 28-bout career.
Buatsi Earns Triumph in Uneventful Affair
The fighter's advancement has plateaued in recent times through contract problems and extended periods of lack of fights.
Previously predicted as the rising talent of UK boxing, he now stands trying to realize his potential - maybe in what feels like a ultimate opportunity - under recent support.
He started carefully, with neither fighter willing to overcommit in a calculated opening few rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second fight at light heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who utilized a protective stance to barely take the more effective periods.
The audience's tolerance diminished because of frequent holding, with Parker going down several times during clinches.
The underdog ended stronger, but many rounds were hard to judge. However, ex-champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just one round.
The victor moves on, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates Manchester Derby Battle
In the co-main event, Arthur beat Rea by divided decision in a outstanding local rivalry fight to capture the European light heavyweight title.
The venue became quiet for a extremely emotional memorial prior to the bout as a bell ceremony sounded in memory of local hero Ricky Hatton, who died aged 46 in September.
It was the first major televised boxing event in the urban center since Hatton's passing. As the last bell faded, the quiet became a chant of "there's only one Hatton".
The action within the ring matched the sentiment. Arthur was sent to the canvas by a powerful punch squarely on the jaw in the initial stage, standing uncertainly to his position on the referee's count.
But the Manchester United-red equipment of Arthur soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged quickly, heavy swelling appearing under his face as the duo traded punishing blows.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace rarely dropped over 12 rounds.
The victor narrowly won the result with judges scorecards of 114-114, narrow lead and clearer margin, but the two athletes were determined and full of heart, everything their inspiration Hatton stood for.
