The Colombian midfielder has picked up a knock in this weekend's Serie A encounter, and will be out of action for a while due to the injury
Head coach Andrea Stramaccioni received the unfortunate news from the treatment table in the aftermath of his side's 3-2 Serie A loss away against Atalanta.
The Colombia international featured for the full 90 minutes in Sunday's defeat, but complained about the muscle problem after the match, then underwent a series of tests which diagnosed him with a thigh strain.
"A first degree strain to the left thigh. This was the verdict on Fredy Guarin, who underwent tests carried out by the Inter medical staff after picking up an injury at the end of the Atalanta v Inter match played Sunday in Bergamo," a statement on the club's official website reads.
It is not yet known exactly how long the 26-year-old will be out of action, but he is unlikely to feature in the upcoming home match against Cagliari.