Mezue ahịrịokwu na-esonụ: Na July 1, 2018, a gbanwere O'Reilly na St. Louis Blues na mgbanwe maka Tage Thompson, Vladimír Sobotka, Patrik Berglund, a
Nhọrọ nke mbụ nke 2019 na nke abụọ nke 2021. Ọ bụ ezie na O'Reilly nwere oge dị elu na ọrụ ya na Blues, ndị otu ahụ dara n'ọnọdụ ikpeazụ gburugburu otu egwuregwu niile site na Jenụwarị 2, na-akpata mgbanwe nchịkwa na onye na-eche nche. Ka ndị Blues laghachiri azụ, O'Reilly nwere afọ ọrụ na afọ mbụ ya na St. Louis, na-enweta ọrụ dị elu na enyemaka na isi ihe ma jikọta ọrụ ya dị elu na ihe mgbaru ọsọ. A kpọrọ ya ka ọ gaa egwuregwu nke abụọ ya na NHL All-Star Game, ebe o debere akara asaa site na egwuregwu abụọ ma bụrụ onye ikpeazụ maka MVP All-Star Game, n'ikpeazụ na-efunahụ Sidney Crosby.