Witherspoon (thigh) will play in Sunday's NFC divisional-round contest versus the Eagles, Jourdan Rodrigue of The Athletic reports.
Witherspoon (thigh) was listed as a non-participant for Wednesday's walkthrough session, Stu Jackson of the Rams' official site reports.
Witherspoon tallied six tackles (five solo) and two pass defenses (including an interception) during the Rams' 13-9 win over the Cardinals on Saturday.
The Rams elevated Witherspoon from the practice squad to the active roster Saturday.
Witherspoon signed with the Rams' practice squad Wednesday.
Witherspoon is slated to sign with the Rams on Wednesday, Jordan Schultz of BleacherReport.com reports.
Witherspoon logged seven total tackles (four solo), including one tackle for loss while also deflecting a pass in Sunday's 26-25 win over the Giants.
Witherspoon (groin) does not carry an injury designation into Thursday's game versus the Saints, Adam Caplan of SiriusXM NFL Radio reports.
Witherspoon (groin) was estimated as a full participant at the Rams' walkthrough practice Tuesday, Adam Caplan of SiriusXM NFL Radio reports.
Coach Sean McVay said Monday that he expects Witherspoon (groin) to play Thursday versus the Saints, Gary Klein of the Los Angeles Times reports.