Cavani has only made 19 appearances in his second season with Manchester United, scoring two goals.
The 35-year-old has not played for the Red Devils since February 8 against Burnley.
He has been consigned to the sidelines on various occasions this season due to various fitness problems but his recent unavailability is due to a thigh problem.
Speaking to United's official website, Cavani said: "Yes, I've been unfortunate to be out through injury, and for a longer period than I'm used to.
"I've never been used to spending this length of time on the sidelines. It's something that I'm finding very difficult, something which is very tough.
"Mentally, it's not easy either, because when you're not used to it, it really is extremely hard to take on board what is happening and seeing your team-mates each game going out on to the pitch, either for training or to play in a match, and you can't be joining them out there.
"It's hard to take, and it's really frustrating that you're feeling like that, and it makes you a bit anxious and really keen to be wanting to be fit and ready as quickly as possible."
Cavani's contract with Man United expires at the end of the season.
