Despite taking eight wickets, Steven Finn was expensive in the final warm-up match in Sydney which might have tilted the balance in favour of Surrey pace bowler Tremlett, who tormented Australia the last time England toured Down Under.
Boyd Rankin picked up four wickets in the Sydney match but may not have done enough to take the third fast-bowler's spot alongside James Anderson and Stuart Broad for Thursday's match in Brisbane.
While the visitors were not happy with the performance of the fast bowlers, they were confident the pacemen could stand up to the challenge, Australia-born Saker said.
"I think we're pretty clear in our minds where we're going to go. I'm not going to announce who's going to play but we're confident where we are," Saker told reporters.
"(Bowlers haven't gone as well as we'd like) But I know that the guys we've got in this group are good enough and we're prepared and we're ready for this challenge.
Saker said Tremlett, who was rested in Sydney, had impressed with his bowling during the practice sessions.
"In the last week, I've seen a big change for Chris Tremlett, so that was a real pleasing thing for us," Saker said. "We did have two or three really good sessions in Sydney. We had a good chat about some certain things.
"The nets were fantastic batting surfaces and he came out of that really well and I think he gained a lot of confidence in where he was."
Injured Tim Bresnan, England's usual choice for the third seamer's role, would play a tour match in Alice Springs after the first test in time to make a comeback in next month's second test in Adelaide, Saker said.
Wicketkeeper Matt Prior, another injury concern for England for Thursday's first test with a calf strain, was also recovering well.
"He's making good progress up to now. Obviously we'd love him on the park on Thursday," Saker added. "He's got a few days to get that right. I'm confident he'll be right but that's for the medical department."
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