As BW mentioned the Carolina Panthers have yet to officially announce this as the standard protocol for these moves is to also announce who is taking the roster spots for players who are going to IR. However, given the breadth of coverage from several local and national sources it's a foregone conclusion.
The Panthers' two rookie DTs represent the 13th and 14th players placed on IR this season, which ties the team record. However, it's important to not throw around too many superlatives or freak out about the injuries. At this time of year if a player has a strain or similar injury you think could take 3-4 weeks to heal then you might as well put them on IR, gain two roster spots and save the players for the next season.
There's no doubt though that the Panthers are in a real predicament here. With only Frank Kearse and Andre Neblett on the roster Carolina are left with just two defensive tackles. However, if you think that Pat or Kevin Williams is the answer here then you're entitled to your opinion, you just don't have an understanding of this organization.
What we'll see is the same as what we've seen all season: The team will scour other team's practice squads, perhaps grab a UDFA and that's it. It doesn't behoove the Panthers to grab a stop gap for a few weeks in a non-playoff year anyway (and no, I'm not entertaining these maniacal "if we win out" wildcard scenarios). Instead the team will likely get some high upside value talent and hope they strike gold, but they probably wont. Kearse and Neblett will start for the remainder of the season and we'll see a few different guys get some time. The DT position will get addressed, but it wont be for another 4 months when free agency and the draft take place.