Captain Alex Rufer responded to recent criticism with an energetic display, while Tim Payne and Clayton Lewis will head into the All Whites camp next week with a spring in their step.
The Phoenix made a bright start. Sandoval looked sharp and dynamic and his presence seemed to open up more space on both flanks, with Reno Piscopo dangerous on the left.
Sandoval wasn't known for his goalscoring in Mexico - being mainly employed on the wing – but managed a crisp finish in the 17th minute, directing a first-time shot into the bottom corner after an intelligent square ball by Hooper.
That was an obvious fillip for the Phoenix, who had only managed one goal across their four previous league games, but they struggled to build on it.
Instead, Western United's experienced unit began to dominate as the Phoenix looked uncertain in their defensive third.
They allowed the Victorian side too much time and space, but the visitors couldn't find the right finish, with Alessandro Diamanti going close and goalkeeper Alex Paulsen kept busy.
The second goal was against the run of play but even better than the first, as Hooper produced a lovely angled finish after being set free by Rufer.
The Phoenix captain twisted away from his marker, before releasing the English striker with a slide run pass.
A point-blank save from Paulsen, when Aleksandar Prijović was probably favoured to score, kept their clean sheet just before halftime.
Diamanti lashed a half volley just wide in the 62nd minute, despite an almost perfect connection, while Hooper blazed over from a similar distance five minutes later, after a sustained period of Phoenix possession.
The Phoenix were getting bodies and blocks in the way, though Jaushua Sotirio drew a full stretch save from Jamie Young, after a swift counter attack, while Christian Theoharous was later denied by a well-positioned Paulsen.
Western United, who were reduced to 10 men in the dying stages, after Tomokai Imai cynically brought down Ben Waine, found a consolation goal through Steve Lustica in the 94th minute but time was always against them.
Earlier, the Wellington Phoenix Women fell to their seventh straight defeat against Adelaide United in the A-League Women.
The Phoenix Women conceded a 68th minute own goal, with Zoe McMeeken credited with the unfortunate final touch after Adelaide right-back Isabel Hodgson sent in a dangerous ball into the box.
Wellington Phoenix 2 (Gael Sandoval 17', Gary Hooper 35')
Western United 1 (Steven Lustica 94')
Halftime 2-0
