Trewin and Australia teammate Aiden O'Neill earned World Cup selection on the strength of their Major League Soccer seasons for New York, and their inside knowledge of Freese is a bonus for Tony Popovic's team.
Trewin said he had spoken to Freese on the day he left for Australia's pre-World Cup camp, but no words had been exchanged since.
"Obviously, there's lots, lots of pressure for him and for the U.S., playing on home soil," 25-year-old Trewin told reporters on Wednesday at the Socceroos' base in Alameda, California.
"So I just wished him the best, and I see how hard he works every day in training and in games. Obviously, I hope we get a positive result against them. But for the rest of the tournament, I wish him the best."
Freese let one goal past him in the World Cup opener against Paraguay, but otherwise enjoyed a fine day as the U.S. dismantled the South Americans 4-1 in front of a fervid home crowd at Los Angeles Stadium.
Australia started their campaign with a 2-0 upset of Turkey, who were seen as the U.S.'s top challengers in the group.
O'Neill was asked whether his teammates had joked about him facing off against Freese.
"I think it was just more - yeah, we're excited to play against each other," he said.
"Obviously, he's a top keeper, Matt, and it would be good to get one up on him, that's for sure."
Australia lost a friendly 2-1 to the U.S. in Denver last October, a physical match that saw the hosts' talisman Christian Pulisic limp off before the half-hour mark after repeated, heavy challenges by hard-nosed defender Jason Geria.
There are questions over Pulisic's fitness for Friday's Group D clash in Seattle after he was taken off at halftime against Paraguay with a calf problem after dominating the South Americans.
The attacker has continued to train separately from the group, teammates said on Wednesday.
Trewin said he was sure Pulisic would face Australia, and his early substitution was only precautionary.
"And I hope he plays," he added. "You want to play against their best 11. So, yeah, I'm sure he'll be fine."