 Following a long rehabilitation program from a broken leg on international duty, Caldow made only four appearances in 1963–64, as Rangers won a domestic treble.He re-established himself in the team at left-back during the 1964–65 season, playing 34 matches.He helped Rangers to a 2–1 League Cup final success against Celtic and to reach the quarter-final of the European Cup, where they lost 3–2 on aggregate (3–1 defeat away, then a 1–0 win at home) to Inter Milan.