Nichols has trained strongly over the past fortnight since overcoming a torn hamstring.
But with a 39-degree scorcher forecast for Sunday in Adelaide, Nichols might be given another week before being thrown back into action.
De Silva could also be left in Perth after missing training on Friday because of illness.
Glory defender Dino Djulbic is suspended following his wrestle last week with Sydney FC's Jacques Faty.
But Rostyn Griffiths will return from his own one-match ban, while Chris Harold is also available after overcoming an ankle injury.
Glory coach Kenny Lowe said he would wait until Saturday before deciding whether to include Nichols.
"You saw today Mitch was on fire. It would be lovely for him to play," Lowe said. "At the end of the day, if he's comfortable mentally and he's ready physically, then he'll be involved.
"If one of those two are not right, then we'll park it and look at it another day."
Adelaide also has injury concerns, with doubts surrounding the availability of Nigel Boogaard (knee), Dylan McGowan (thigh), Marcelo Carrusca (calf) and Bruce Djite (ankle).
Glory's lead at the top of the table has been cut from seven points to one after a draw and two losses from its past three home games.
Adelaide has proven to be its bogey side this season, with Glory losing three times to the FFA Cup winner.
Lowe said even a draw would be a decent result for Glory.
"Anything's good in Adelaide. They're a good side," Lowe said. "It's a big game for them ... so I think the pressure is on them a little bit."
