[3][4] His personal best of 22.90 m (75 ft 1+1⁄2 in), set in Doha, 5 October 2019, is also the Oceanian record and makes him the seventh best shot putter in history.

Walsh made his international debut at the 2009 World Youth Championships in Athletics, where he placed sixth in his shot put speciality and also competed in the qualifying of the discus throw.

[5] On 12 December 2009 Walsh recorded a put of 20.21 m (66 ft 3+1⁄2 in) the 5 kg shot to win the Senior Boys title at the New Zealand National Secondary School Track and Field Championships.

This performance was a New Zealand Youth (Under 18) record which was broken the following day by Jacko Gill when winning the Junior Boys (Under 16) title.

At the 2010 World Junior Championships in Athletics Walsh failed to qualify for the final of the shot put which was won by Gill.

He surpassed this with 22.67m on 25 March the same year, at the Sir Graeme Douglas International Track Challenge in West Auckland, New Zealand, moving him into the top-10 World All-Time.