Another man making his Phoenix debut, Stein Huysegems, had earlier given the Phoenix the lead in the 43rd minute with a beautifully-taken finish that gave Sydney goalkeeper Ivan Necevski no chance.
Huysegems, who joined the Phoenix after spells in the Dutch and Belgian leagues, looked rusty in the early stages as he struggled to connect with a couple of opportunities to head home, but his goal just before half-time showed he is a player of true quality.
All the pre-match hype surrounded Sydney FC's big-name acquisition Alessandro Del Piero, who had ventured down under for big money after 19 seasons with Italian giants Juventus.
The 37-year-old clearly lacked match-fitness and barely touched the ball until the 14th minute, but when he did everyone at Westpac Stadium was reminded of his class.
He skipped past two Phoenix defenders and unleashed a right-foot strike, which never really threatened Mark Paston's goal, but gave an indication of the danger he posed.
In between a few other touches, the 2006 World Cup-winner showed he still possesses plenty of skill and when he gets up to speed with his new team-mates and the league, he will be a force to be reckoned with.
In the opening spell, the Phoenix made all the head way, with a new look front half of the pitch with Benjamin Totori and Fenton on the flanks, while Jeremy Brockie and Huysegems roamed free up front.
Chance after chance fell to the home side, who rattled the post via Totori, while Brockie and Huysegems both spurned good scoring opportunities.
Eventually, Totori was pulled after 61 minutes following an encouraging debut for the Phoenix, although coach Ricki Herbert may have been concerned with how often the Solomon Islands international went to ground when challenged physically.
Totori's replacement was the popular Ifill, who nearly scored with his first touch of the ball, but Necevski made a fine save with his feet.
In the end it was left to Fenton to make the game safe for the Phoenix and the young man couldn't have written a better script himself.
Wellington Phoenix 2 (Stein Huysegems 43, Louis Fenton 75) Sydney FC 0 HT: 1-0