Grigar credits two-time Olympic Champion Elena Kaliská with helping him in his early years and showing him that canoe slalom is fun.

He qualified for the 2016 Summer Olympics in Rio de Janeiro, beating his more experienced teammates Halčin and Málek in the internal qualification.

[5] Returning from his best form in 2021, Griger claimed his first World Cup victory in Markkleeberg in June, en route to a silver medal at the delayed 2020 Summer Olympics in Tokyo.

He was also part of the silver medal winning K1 team at the 2021 ICF Canoe Slalom World Championships with Martin Halčin and Adam Gonšenica.

2023 did not yield any medals for Grigar, but he did manage to qualify for his third Olympics, beating Martin Halčin by a single point in the internal qualification.