Agustien follows Lee Carsley and Marcus Bent into the Blues squad, but McLeish is on the look out for more new signings ahead of the new season which starts against Sheffield United at St Andrew's on August 9.
"I'm trying to do some deals at the moment to give the fans a bit of interest," he told the Blues website.
"It's gone a wee bit quiet but I'm hopeful we can make announcements this week so we can go into the season with a strong squad and great optimism."
McLeish added: "At the moment we've got 17 players, including two goalkeepers.
"We are looking at having a squad of 20 senior players and then we'll work the loan system or bring in two or three young players.
"I have been in touch with one of two Premier League managers about loans but one or two players I asked about were unavailable."




