It was as an Academical player that Maclagan was first chosen to represent the Scotland national team. Although he would later play his rugby at three-quarter, Maclagan was placed at fullback when chosen to face England in 1878. The next season Maclagan was again selected at fullback, and after a win against Ireland, in only the second encounter between the two countries; Maclagan again faced England in the very first challenge for the Calcutta Cup. The England game was a dull 3–3 draw, but Maclagan was deemed to have served his team with outstanding play.Griffiths (1987), pg 2:4. He tackled bravely throughout the match, upsetting numerous English attacks.
