Cameroon's Bryan Mbeumo to miss Africa Cup of Nations after ankle surgery
Mbeumo had stepped up in the absence of banned striker Ivan Toney to top the scoring charts for Brentford with seven goals and three assists in the league this season.
But the Cameroon international limped off the pitch after rolling his ankle against Brighton & Hove Albion earlier this month, adding to a long list of injuries at Brentford.
"(Mbeumo) will not participate in the Africa Cup of Nations," Frank said.
"Bryan is a positive guy. It's tough to take, but he will come back stronger. He has a very good mindset."
The Africa Cup of Nations kicks off on January 13th with five-time champions Cameroon in Group C along with Senegal, Guinea and Gambia.
Brentford have dropped to 11th in the league after one win and four defeats in their last five games.
With Rico Henry, Kevin Schade, Aaron Hickey and Kristoffer Ajer also sidelined, Frank said they would look for reinforcements in January.
"Almost from game one we've struggled a little bit with injuries. But we still have a good group of players who are willing to fight," he said.
"We need to look at it in January, but we never rush into things. We try to be clever and take calm and sensible decisions. We will not take a player if we don't think it's for the longer term.
"Maybe this time a loan, but it depends on how things go over the next three or four weeks."