Kris Boyd and Kevin Thomson has joined Middlesbrough, while Steve Smith, DaMarcus Beasley and Nacho Novo left Ibrox in the summer."Injuries and suspensions that bother me right now, and more than ever before," said 62-year-old Smith.
"In fact, they do worry me most, as I look towards the new season."
Rangers travel to Australia on Tuesday to continue their pre-season training to defend their Scottish Premier League title.
Left-back Papac Sasha unavailable after suffering a knee injury in last weekend friendly against Queen of the South.
And Smith, who in his last season as a manager at Ibrox, is seeking to strengthen his squad before seeking a third league championship.