British light heavyweight Joshua Buatsi made a winning yet underwhelming start to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a tight ten-round bout at the boxing arena.
But the challenger landed significant shots, delivering effective individual punches in a fight where the techniques failed to mesh, with frequent clinching marring the action.
The officials had it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They win," Buatsi commented in the ringside as he was greeted with disapproval from the audience.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, merited the win but the contender endured the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Slow Affair
His career development has plateaued in the past few years through promotional disputes and considerable time of lack of fights.
Once tipped as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to take risks in a calculated initial rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second fight at light heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who worked behind a solid defense to narrowly win the more effective stanzas.
The audience's tolerance decreased because of constant clinching, with Parker falling to the floor several times during grappling.
Parker closed well, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the co-main event, Arthur beat Rea by close verdict in a terrific local rivalry contest to secure the European light-heavyweight championship.
The arena grew hushed for a extremely emotional homage prior to the bout as ten bells tolled in honor of Manchester's own Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the urban center since Hatton's death. As the final chime ended, the quiet gave way to a shout of "only one Ricky Hatton".
The competition within the ring equaled the feeling. The eventual winner was knocked down by a powerful punch squarely on the chin in the second round, rising shakily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up quickly, noticeable damage appearing under his orbital area as the pair exchanged hard punches.
Rea, 27, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the intensity rarely dropped over 12 rounds.
The victor edged the verdict with official scores of draw, close margin and clearer margin, but each competitor were relentless and courageous, everything their idol Hatton embodied.
