Thomas Frank says it would take an "unbelievable price" for Brentford to sell Ivan Toney.
The forward is available for Brentford's next Premier League match against Nottingham Forest on 20 January, after his eight-month suspension for betting-related charges ends on 17 January.
Toney is also being linked with a move away from the club in the January transfer window.
"He's a Brentford player, he's here," head coach Frank told the club's official website. "Clearly, we have missed a few offensive players and I can't see why we should sell him. I would love to have him here for a long time.
"If I could ever, ever, ever recommend something, and it's not for me to say 'yes' or 'no', that's up to Phil Giles [director of football] and Matthew Benham [owner]. I would say it needs to be an unbelievable price."
Toney scored 20 goals in 33 Premier League appearances last season, playing a crucial role in the Bees' impressive ninth-place finish.
His return is timely for Brentford as leading scorer Bryan Mbeumo is currently sidelined with an ankle injury, while fellow forward Yoane Wissa has joined up with DR Congo for the Africa Cup of Nations.
Frank expects Brentford to be active in the January transfer window, with a new left-back a priority given Rico Henry's long-term knee injury.
“I'm convinced that we will be active in the market. How much? Which position? Let's see," he added.
“I expect that we will be active, and I think it's pretty clear that we, most likely, need a left-back.”
A run of seven defeats in their last eight matches has seen Brentford slip to 16th place, only four points above the relegation zone.