Kembali
Sebastien Pocognoli's side face North Macedonia at Hampden and Switzerland in St Gallen in the final two games of the campaign.
McKenna played three out of the four games in the group before he was sent off during Scotland's win in North Macedonia and therefore suspended for the defeat to Slovenia in Glasgow.
He missed Dinamo Zagreb's midweek league win over Rijeka with a back strain picked up in training, but his Croatian club were hopeful he would return for their league game at the weekend against Rudes and Europa League match in Sunderland on Thursday.
But manager Mario Kovacevic has now revealed McKenna won't be available until after the international break.
He said: "Scott McKenna will most likely be out for two weeks due to his injury, so he will be out until after the break."
And Scotland seem unlikely to risk the former Aberdeen and Nottingham Forest stopper for the final two games in the section.