"Keep our fingers crossed that heâll be back. When it will be, I canât tell you for sure," Shanahan told the paper.
Cooley, who has practiced off and on, had arthroscopic surgery on the knee after last season but has experienced swelling and irritation.
As for when Cooley will return, "Weâll just have to wait and see," Shanahan said.
"Heâs had it drained a few times. Thatâs not good. Heâs a tough player and he wants to get back quick. We have to give him a little break and hopefully weâll get the knee responding."