For the third time in as many days, wide receiver and kick returner Tavon Austin (ankle) and cornerback Janoris Jenkins (back) sat out practice Friday at Rams Park. Austin, who was hurt at the end of a 56-yard run last weekend in Arizona, was again in a walking boot Friday to protect his left ankle. “He’s questionable (for Sunday); that’s 50-50,’’ Rams coach Jeff Fisher said following Friday’s workout. The Rams’ injury report also lists Jenkins, running back Daryl Richardson (thigh) and guard Harvey Dahl (knee) as questionable for Sunday’s 3:25 p.m. game against the NFC South-leading New Orleans Saints at the Edward Jones Dome. Richardson and Dahl also sat out practice Friday. Dahl returned to action last week after missing the previous four games with a knee injury. After sitting out Wednesday, rookie cornerback Brandon McGee (foot) was a full participant in Friday’s practice and is probable for Sunday. If Austin cannot play, possible replacements on kickoffs are Benny Cunningham, Isaiah Pead and Chris Givens. Austin Pettis is second on the unofficial depth chart on punt returns. The only New Orleans starter on the Friday injury list is defensive tackle Brodrick Bunkley (back), who practiced Friday and is listed as questionable for Sunday. Other Saints listed as questionable are safety Rafael Bush (ankle), tight end Josh Hill (hamstring), linebacker Keyunta Dawson (calf), tackle Terron Armstead (nose) and defensive end Glenn Foster (knee).