Liverpool host Chelsea at 16:30 BST on Sunday before a Champions League game away at RB Leipzig on Wednesday.
Alisson has already missed two games this season through injury and was out for more than two months from February to April last season.
“It’s a bit uncommon for goalkeepers,” said Slot. “For me, it’s common because the goalkeeper I had at Feyenoord [Justin Bijlow] also had his issues with injury, also muscle injuries. That’s not what you see a lot, so these two are more of an exception.
“We are looking into it and what could be the reason.
“One of the things that we all know is that if you’ve had one, then the chances of getting another one always go up so we’ve tried to be really careful with him.”
Alisson, 32, will miss his side’s league game against Chelsea on Sunday along with top-flight matches against Arsenal, Brighton and Aston Villa, Champions League meetings with RB Leipzig and Bayer Leverkusen and a Carabao Cup game against Brighton.
Irish keeper Caoimhin Kelleher is expected to play for the Reds.