Aberdeen could be without midfielder Kari Arnason for up to six weeks after he suffered a hamstring injury.
The Iceland international sustained a tear during training and will undergo a scan to discover the extent of the problem.
Arnason will definitely miss games against Motherwell and Dunfermline, with the best case scenario likely to be an absence of three weeks.
The summer arrival has been an instant hit at Pittodrie with manager Craig Brown and Dons supporters urging the club's board to extend the 29-year-old's one-year deal.
His form has also led to talk of a recall to the Iceland national side.
Brown is reluctant to speculate on how long Arnason will be sidelined for, but was happy to have avoided a selection dilemma on Monday when the Dons' SPL meeting with St Johnstone was called off due to fog.
He told RedTV: "The hamstring injury is one which does take a bit more time than some of the others.
"So we have to get it properly and carefully checked, possibly with a scan just to confirm the extent of the injury.
"He wouldn't have been able to play last night so that means we would have had two midfield players out - Rob Milsom and Arnason.
"We are disappointed the game was postponed but, with it being postponed, it will give both these injured players a little more time to be ready for the re-arranged fixture."
St Johnstone wanted to make use of a free weekend by re-arranging the fixture for this coming Saturday.
But with Mohamed Chalali, Josh Magennis, Peter Pawlett and Ryan Jack - suspended for the clash with Saints - all on international duty, the Dons refused the request.
Brown added: "We've got four players away on international duty so it would be crazy of us to agree to play the fixture with four players away on international duty and two doubtful through injury."