Martinez dismissed suggestions Gibson, who had played only 96 minutes for his club this season because of another knee problem, had been overworked on international duty.
"If it has been in the 80th minute then you can go down to detail and see if fatigue played a part in it," said Martinez.
"When you watch it is so unfortunate the knee couldn't react any other way, so clearly it is one of those unexpected moments that you can't do anything about.
"I expected the worst and thought it would be a very difficult injury to overcome but now we are very positive and know Darron will be fully fit and recovered and will come back a stronger footballer at the end of it."
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