Jackson missed the 28-16 loss to the New York Giants with a right quad injury after an unsatisfactory pregame warmup.
Jackson's replacement, Cadillac Williams, tweaked his hamstring against the Giants and Spagnuolo categorized him day to day.
Wide receiver Danny Amendola, quarterback Sam Bradford's top target, also missed Monday's game and is day to day with a dislocated left elbow. Spagnuolo said swelling was down and Amendola already had improved range of motion.
They'll need Amendola back as soon as he's ready after Greg Salas suffered a rib injury. Salas was undergoing a CT scan after X-rays did not indicate a break.
Even wide receiver Danario Alexander, who caught three passes for 122 yards and a touchdown Monday, saw limited action against the Giants because of knee issues.
Alexander has undergone five operations on his left knee and was inactive for the opener.
Spagnuolo said his practice time was being closely monitored to avoid irritating the knee.
The Rams also lost another cornerback, with Tim Atchison sidelined indefinitely with a hamstring injury. The team was thin in the secondary before cornerback Ron Bartell was lost for the season in the opener with two fractures in his neck.
Linebacker Ben Leber (groin strain) is day to day.
Information from The Associated Press contributed to this report.