All-Pro linebacker Patrick Willis is scheduled to undergo an MRI examination Monday on his groin 49ers coach Jim Harbaugh said.

Willis who sustained the injury while in pursuit of Indianapolis Colts wide receiver Reggie Wayne on a late-third quarter play is not expected to be ready for the 49ers’ game Thursday night against the St. Louis Rams.

Said Harbaugh “We’ll leave that to the evaluation and the opinion of the doctors.”

Third cornerback Nnamdi Asomugha is also scheduled to undergo an MRI on his right knee Harbaugh said. Asomugha was injured on a fourth-quarter play while tackling Colts running back Ahmad Bradshaw.

The 49ers will continue to evaluate tight end Vernon Davis who sat out Sunday’s 27-7 loss to the Indianapolis Colts with a left hamstring strain. Harbaugh said it is not known whether Davis will be available to play against the Rams.

One player who definitely will not be available is outside linebacker Aldon Smith who reportedly was on his way to undergo treatment for substance abuse. Smith was arrested Friday morning on suspicion of driving under the influence and possession of marijuana.