After two months out with a calf injury, Tupou's return was patchy in Australia's 25-17 second-Test loss in Brisbane.
He crashed over for a first-half try but his tight work was inconsistent and he was pinged for four penalties.
Ideally Tupou would have eased his way back from the bench but Alaalatoa was unavailable after suffering a head-knock in the opening Test win, leaving the Wallabies' tighthead prop pool thin.
Alaalatoa has completed the new 12-day concussion stand-down protocol and the Brumbies skipper is set to return.
Wallabies assistant coach Dan McKellar said he was happy with what Tupou brought to the Brisbane Test, and predicted a better showing at the SCG on Saturday with the Ella-Mobbs trophy on the line.
"Taniela, first game back after a long period out, he did some really good things," McKellar said.
"I thought his ball-carrying was was excellent and he will have learnt a couple of things in and around scrum and what the English tactics were there and will be better for the run.
"With 50 minutes of footy on board now ... there's no doubt he'll be in a better place Saturday night.
"It's good to have two quality tighthead props back available to help share the workload."
Asked whether crafty England coach Eddie Jones may have worded up referee Andrew Brace about Tupou's scrum technique, McKellar said he wasn't sure.
"Coaches will have conversations with referees every week and I'm sure Eddie's no different," McKellar said.
"Whether he spoke specifically about Taniela I can't answer that."
Ex-Queensland Reds lock Lukhan Salakaia-Loto joined the squad on Monday from club rugby as injury cover and has impressed McKellar.
The 30-Test veteran was unwanted by the Wallabies at the start of the series after being on the outer at the Reds.
"Pleasingly he's just got on with it and dealt with his non-selection," said McKellar.
"He put his hand up to play for his club in Souths which is great in terms of his attitude.
"He looks to be in pretty good shape, he's looked after himself ... so he certainly hasn't dropped the ball in terms of his conditioning.
"It's obviously a step-up in intensity and physicality and the pace of the game (from club rugby) but he's been there before and can call on that experience."
