Jafar Armstrong suffered a groin injury early in the first quarter, a source tells The Athletic.That’s why you’ve been seeing a large amount of red-shirt freshman running back Jahmir Smith.— Pete Sampson (@PeteSampson_) September 3, 2019There’s no word yet on the severity of the groin issue Armstrong is dealing with, but it clearly behooves Notre Dame to be cautious here.Jones is already over 100 yards rushing, and both he and Smith have found the end zone. The Notre Dame ground game is still working fine without Armstrong.However, the ninth-ranked Irish find themselves in a dogfight, leading Louisville 21-14 midway through the third quarter.You can catch the action on ESPN. SOUTH BEND, IN – SEPTEMBER 01: Khaleke Hudson #7 of the Michigan Wolverines tackles Jafar Armstrong #8 of the Notre Dame Fighting Irish in the first quarter at Notre Dame Stadium on September 1, 2018 in South Bend, Indiana. (Photo by Gregory Shamus/Getty Images)Notre Dame fans watching tonight’s game against Louisville are all wondering what happened to running back Jafar Armstrong.Armstrong, who was a key contributor in the backfield last season after moving from wide receiver, played a key role on Notre Dame’s opening drive. He carried twice for 10 yards and caught one pass for 16 yards as the Irish moved downfield for a touchdown.However, after that series, Armstrong hasn’t seen the field. Notre Dame has been using Tony Jones Jr. and Jahmir Smith, and concerned Irish fans weren’t sure why.Now, it looks like we have an answer. According to The Athletic’s Pete Sampson, Armstrong suffered a groin injury in the first quarter.