The UFC has not, nor has Cruz’s people or Cruz himself, confirmed the injury as of yet but several websites have confirmed the injury. No knowledge to the severity of the injury, or whether or not it officially was an ACL tear or another form of knee injury, has been confirmed either.
We’ll have more as it breaks.
UPDATE: Dana White just confirmed Cruz blew out his ACL via his twitter feed.
Second Update: Apparently Cruz was hurt last Thursday, a handful of outlets reporting that it was during a practice but again nothing confirmed.