[7] A fortnight later, he agreed to join Premier League side Newcastle United as assistant to Steve McClaren, the recently appointed manager.

[8] When McClaren was sacked by Newcastle United in March 2016 and replaced by Rafa Benítez,[9] Cathro was thought highly enough of to be retained as assistant manager.

Kilmarnock player Kris Boyd questioned whether such a young manager, with limited playing experience, could command the respect of the squad.

[12][14] Celtic manager Brendan Rodgers said that there appeared to be a "confused" approach at Hearts, with a mismatch between the style of play Cathro wanted to implement and the type of players signed by the club.

[18] On 3 July 2021, Cathro followed former-Wolves manager Nuno to Tottenham Hotspur, after being appointed assistant head coach.