Usual captain Kosovare Asllani is awaiting cruciate ligament surgery, while vice-captain Nathalie Bjorn, is also out of the qualifiers through injury.
Head coach Tony Gustavsson has handed the armband to 30-year-old Blackstenius for home games against Denmark in Gothenburg on 14th April and Serbia in Solna four days later.
"A very experienced player who knows what it means to play important matches, and who is always herself both on and off the field," Gustavsson said of Blackstenius.
That experience will be tested after Sweden began their campaign with a 1-0 away win against Italy before labouring to a 0-0 draw in Serbia. Second in Group A1, Sweden will be targeting points at home - especially against current leaders Denmark - if they are going to take the automatic qualifying spot.
The pressure of leadership is not put on just one pair of shoulders in the national team. Gustavsson prefers to have one leader on the pitch for each of the four main positions on the field, and the choice of who is the designated captain is very simple.
"The player who wears the armband in each match is the one with the most international caps," the coach explains. Blackstenius has been capped 125 times so far.
What is not so simple, however, is keeping those key players fit. Johanna Rytting Kaneryd has joined up with the squad, but has not been training with the rest of the squad owing to a calf injury that kept her out of recent matches for her club, Chelsea.
"The information I have received is that right now it is day-to-day. When we get closer to the match and there is a decision, the medical team will inform me. Then we will have to make a decision whether we have to replace her in the squad or if she can sit on the bench," said Gustavsson.
Should the forward not play, Blagult will be down to just five players who have been capped 50 times or more ahead of the key qualifiers.