The Chile international was forced off during the closing stages of the goalless draw at West Brom on Monday night with a twisted ankle and Rovers have confirmed he is now set for a spell on the sidelines.
Blackburn boss Tony Mowbray did not put a timescale on the 20-goal forward’s recovery, but said he will miss the Sky Bet Championship match against Millwall on Saturday.
Mowbray said: “He’s okay, in a good mood, joking around as he normally does.
“He has twisted his ankle, it wasn’t a kick, and he will miss a period of time.
“We will wait and see how long that will be.
“He won’t be available this weekend which is a blow but it’s an opportunity for someone else to come in and see if they can knock the goals in.”
Meanwhile, Millwall will check on Oliver Burke ahead of the trip to Lancashire.
The forward, on-loan from the Blades, came off during the first half of the home win over QPR on Tuesday night with a hamstring injury, and continues to be monitored.