The Blackpool defender has pulled out of the squad after failing to recover in time for the upcoming matches against Portugal and Luxembourg.
Manager Michael O'Neill has given himself more options by calling up versatile Aberdeen player Josh Magennis and Kilmarnock defender Rory McKeown.
The absence of Cathcart and suspended Burnley defender Daniel Lafferty means O'Neill will make at least two changes to the side which claimed an upset 1-0 win over Russia last month.
Manchester United's Jonny Evans and fellow defender Ryan McGivern of Hibernian are expected to come in as Northern Ireland host Portugal in Belfast on Friday and travel to face Luxembourg four days later.
O'Neill's side are fourth in Group F on six points, five behind third-placed Israel and eight adrift of leaders Portugal, having played a game less than the pacesetters.