Gombau said he expects the trio to sign two-year contract extensions this week.
"All three are agreed in everything. If everything is normal, next week we can announce that these players will be with us two more seasons," he said.
"We are not doing just one season, we are signing for two and that will be good because it means we can work with a project, think long-term, two years in front.
"The players want to be here, they are happy with the club, happy with the city - as a coach it means a lot because you can make a plan."
Another trio - Nigel Boogard, Osama Malik and Cameron Watson - were all weighing up offers with Gombau hoping to retain "95 per cent" of his squad beyond the season's end.
Third-placed Adelaide is four points adrift of Perth believes its ambitions of topping the league hinge on the result.
"For us this is like the final of the league," Gombau said.
"After this game, if we win we will be in the top three fighting for something nice. And if we don't win, the gap is seven points and it's a lot.
"Tomorrow is a game, I have said to the players, that we need to think of as a final - and win this final playing at home."
Gombau said he was expecting a fired-up Perth, which on Thursday was hit with show cause notices from Football Federation Australia (FFA).
FFA alleged breaches involve failure to disclose benefits to players including accommodation costs and car allowances for the past three seasons.
Perth hasn't beaten Adelaide in their past eight meetings, including this year's FFA Cup final and two A-League clashes.
"All the games we have played against them this year we win, but just from small details," Gombau said.