 Jääger made his senior league debut in the Esiliiga on 2 April 2000, playing for Flora affiliated Lelle in a 1–3 home loss to Merkuur Tartu.In December 2000, he moved to Flora's reserve side Valga.Jääger made his Flora – and Meistriliiga – debut on 4 November 2001, in a 3–0 away victory over Lootus.