The 33-year-old former Wales international has been sidelined with knee and hip problems and has made just seven first-team appearances in the past 18 months,
Davies came through a midweek reserve team outing unscathed as he steps up his fight for fitness.
The ex-Tottenham winger knows he needs to hit the ground running if he is to earn a new deal at Craven Cottage.
Manager Martin Jol said: "Simon is almost a project and it will be good to have him back.
"We will ease him back in slowly as he is still a few weeks away from rejoining the first team.
"He has been so unlucky. Fingers crossed he can now stay injury-free."