The 31-year-old reportedly contracted his national team boss to tell him he would be absent for their double header against Austria and Bosnia-Herzegovina.
O’Neill said Lafferty had “ruled himself out of the two games” and added: “Our focus is the players who are with us. I’ll address the situation after the international period.”
Lafferty, who re-joined Rangers from Hearts in August, has scored and created 59 goals in 143 games over two stints and has started the new season strongly under Steven Gerrard – four goals in eight Premiership games.
The former Burnley, Norwich and Birmingham striker has represented the Northern Ireland national on 68 occasions, scoring 20 goals, but he’ll now miss two of their upcoming fixtures.
In Lafferty’s stead, Rotherham United striker Kyle Vassell was given his first call-up. BBC Sport says the 25-year-old, who scored 13 goals as his Blackpool side won promotion to League One last season, is qualified to play for Northern Ireland through his Fermanagh-born grandfather.
Elsewhere, Charlton Athletic’s Jamie Ward dropped out of the side to work on his fitness while Aberdeen’s Niall McGinn is absent with a hip injury. Vassell has led a nomadic career up until now but he’s finally being rewarded for his fine form.
Stats from Transfermarkt.